Subscriptions not found when having AAD B2C setup

**Describe the bug**
When running:
`az login`

It gives the warning

> "The following tenants don't contain accessible subscriptions. Use 'az login --allow-no-subscriptions' to have tenant level access. 15ce3ddb-0ba0-4110-92f6-6f3da6910357"

It does not actually login.

In order for it to work I need to provide my tenant:
`az login -t egelke.net`

**To Reproduce**
Setup an AAD *B2C* as specified by the doc: https://docs.microsoft.com/en-us/azure/active-directory-b2c/tutorial-create-tenant
Note that is did it quite a while ago and at that time it was mandatory to first create your tenant and then link it to your existing subscription.

Set the default directory in the azure portal to the corporate (not B2C) directory.

Run:
`az login`

You should get the warning and not be logged in.
Note that it might work in your case depending on the order the tenants are returned by the the `https://management.azure.com/tenants?api-version=2020-01-01` service.

**Expected behavior**
To find my subscription, without having to specify the tenant.

It is a very standard setup, I just have the ADD B2C service enabled in the documented way. There should be no issue for the CLI to handle this situation without the need provide any additional info.

**Environment summary**
Linux-5.4.0-40-generic-x86_64-with-debian-bullseye-sid
Python 3.6.10
Installer: DEB
{
"azure-cli": "2.8.0",
"azure-cli-command-modules-nspkg": "2.0.3",
"azure-cli-core": "2.8.0",
"azure-cli-nspkg": "3.0.4",
"azure-cli-telemetry": "1.0.4",
"extensions": {}
}

**Additional context**
`az login --debug` learned that it first retrieves the list of tenant and then retrieves the subscriptions from both tenants. The first egelke.net tanant returns my subscription, but although the AAD B2C tenant (egelkeIdp.onmicrosoft.com) is linked to the same subscription the service does not return it. (I verified everyting via https://docs.microsoft.com/en-us/rest/api/resources/)
In this particular case the CLI seems to have "forgotten" the subscriptions returned by the first tenant while it should have merged the 2 lists and find the sole subscription.

Below a snipped of the logs:
> urllib3.connectionpool : Starting new HTTPS connection (1): management.azure.com:443
urllib3.connectionpool : https://management.azure.com:443 "GET /tenants?api-version=2019-06-01 HTTP/1.1" 200 348
msrest.http_logger : Response status: 200
msrest.http_logger : Response headers:
msrest.http_logger : 'Cache-Control': 'no-cache'
msrest.http_logger : 'Pragma': 'no-cache'
msrest.http_logger : 'Content-Type': 'application/json; charset=utf-8'
--snip--
msrest.http_logger : 'Date': 'Thu, 16 Jul 2020 06:41:04 GMT'
msrest.http_logger : 'Content-Length': '348'
msrest.http_logger : Response content:
msrest.http_logger : {"value":[{"id":"/tenants/7aed0c3e-dc7c-4ac0-8e6b-c8cb344472fa","tenantId":"7aed0c3e-dc7c-4ac0-8e6b-c8cb344472fa","countryCode":"BE","displayName":"Egelke BVBA","domains":["egelke.net","share.egelke.net","www.egelke.net","egelke.onmicrosoft.com"],"tenantCategory":"Home"},{"id":"/tenants/15ce3ddb-0ba0-4110-92f6-6f3da6910357","tenantId":"15ce3ddb-0ba0-4110-92f6-6f3da6910357","countryCode":"BE","displayName":"Egelke BVBA","domains":["egelkeIdp.onmicrosoft.com"],"tenantCategory":"Home"}]}
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - Authority:Performing instance discovery: ...
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - Authority:Performing static instance discovery
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - Authority:Authority validated via static instance discovery
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - TokenRequest:Getting token from cache with refresh if necessary.
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - CacheDriver:finding with query keys: {'_clientId': '...', 'userId': '...'}
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - CacheDriver:Looking for potential cache entries: {'_clientId': '...', 'userId': '...'}
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - CacheDriver:Found 3 potential entries.
adal-python : 009b4e6a-42c1-4525-98e8-72a9ba9be42f - CacheDriver:Resource specific token found.
--snip--
msrest.universal_http.requests : Configuring retry: max_retries=4, backoff_factor=0.8, max_backoff=90
msrest.async_paging : Paging async iterator protocol is not available for SubscriptionPaged
msrest.http_logger : Request URL: 'https://management.azure.com/subscriptions?api-version=2019-06-01'
msrest.http_logger : Request method: 'GET'
msrest.http_logger : Request headers:
msrest.http_logger : 'Accept': 'application/json'
msrest.http_logger : 'accept-language': 'en-US'
msrest.http_logger : 'User-Agent': 'python/3.6.10 (Linux-5.4.0-40-generic-x86_64-with-debian-bullseye-sid) msrest/0.6.9 msrest_azure/0.6.3 azure-mgmt-resource/10.0.0 Azure-SDK-For-Python AZURECLI/2.8.0 (DEB)'
msrest.http_logger : Request body:
msrest.http_logger : None
msrest.universal_http : Configuring redirects: allow=True, max=30
msrest.universal_http : Configuring request: timeout=100, verify=True, cert=None
msrest.universal_http : Configuring proxies: ''
msrest.universal_http : Evaluate proxies against ENV settings: True
urllib3.connectionpool : Starting new HTTPS connection (1): management.azure.com:443
urllib3.connectionpool : https://management.azure.com:443 "GET /subscriptions?api-version=2019-06-01 HTTP/1.1" 200 431
msrest.http_logger : Response status: 200
msrest.http_logger : Response headers:
msrest.http_logger : 'Cache-Control': 'no-cache'
msrest.http_logger : 'Pragma': 'no-cache'
msrest.http_logger : 'Content-Type': 'application/json; charset=utf-8'
--snip--
msrest.http_logger : 'Date': 'Thu, 16 Jul 2020 06:41:05 GMT'
msrest.http_logger : 'Content-Length': '431'
msrest.http_logger : Response content:
msrest.http_logger : {"value":[{"id":"/subscriptions/09aa7e5c-38b1-4cad-b283-e2aa6c411d25","authorizationSource":"Legacy, RoleBased","managedByTenants":[],"subscriptionId":"09aa7e5c-38b1-4cad-b283-e2aa6c411d25","tenantId":"7aed0c3e-dc7c-4ac0-8e6b-c8cb344472fa","displayName":"Betalen per gebruik","state":"Enabled","subscriptionPolicies":{"locationPlacementId":"Public_2014-09-01","quotaId":"PayAsYouGo_2014-09-01","spendingLimit":"Off"}}],"count":{"type":"Total","value":1}}
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - Authority:Performing instance discovery: ...
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - Authority:Performing static instance discovery
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - Authority:Authority validated via static instance discovery
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - TokenRequest:Getting token from cache with refresh if necessary.
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - CacheDriver:finding with query keys: {'_clientId': '...', 'userId': '...'}
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - CacheDriver:Looking for potential cache entries: {'_clientId': '...', 'userId': '...'}
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - CacheDriver:Found 3 potential entries.
adal-python : 2ade8d89-485d-4d7b-9c56-ac8ea1b5ed13 - CacheDriver:Resource specific token found.
--snip--
msrest.universal_http.requests : Configuring retry: max_retries=4, backoff_factor=0.8, max_backoff=90
msrest.async_paging : Paging async iterator protocol is not available for SubscriptionPaged
msrest.http_logger : Request URL: 'https://management.azure.com/subscriptions?api-version=2019-06-01'
msrest.http_logger : Request method: 'GET'
msrest.http_logger : Request headers:
msrest.http_logger : 'Accept': 'application/json'
msrest.http_logger : 'accept-language': 'en-US'
msrest.http_logger : 'User-Agent': 'python/3.6.10 (Linux-5.4.0-40-generic-x86_64-with-debian-bullseye-sid) msrest/0.6.9 msrest_azure/0.6.3 azure-mgmt-resource/10.0.0 Azure-SDK-For-Python AZURECLI/2.8.0 (DEB)'
msrest.http_logger : Request body:
msrest.http_logger : None
msrest.universal_http : Configuring redirects: allow=True, max=30
msrest.universal_http : Configuring request: timeout=100, verify=True, cert=None
msrest.universal_http : Configuring proxies: ''
msrest.universal_http : Evaluate proxies against ENV settings: True
urllib3.connectionpool : Starting new HTTPS connection (1): management.azure.com:443
urllib3.connectionpool : https://management.azure.com:443 "GET /subscriptions?api-version=2019-06-01 HTTP/1.1" 200 161
msrest.http_logger : Response status: 200
msrest.http_logger : Response headers:
msrest.http_logger : 'Cache-Control': 'no-cache'
msrest.http_logger : 'Pragma': 'no-cache'
msrest.http_logger : 'Content-Type': 'application/json; charset=utf-8'
--snip--
msrest.http_logger : 'Date': 'Thu, 16 Jul 2020 06:41:05 GMT'
msrest.http_logger : 'Content-Length': '161'
msrest.http_logger : Response content:
msrest.http_logger : {"value":[],"count":{"type":"Total","value":0}}
The following tenants don't contain accessible subscriptions. Use 'az login --allow-no-subscriptions' to have tenant level access.
15ce3ddb-0ba0-4110-92f6-6f3da6910357