Cannot login with Service Principal secret on Azure Stack Hub

**Describe the bug**
When I try to login to the Azure Stack Hub Tenant ARM endpoint using version 2.30.0 of the CLI I get this error:

```
MSIS9605: The client is not allowed to access the requested resource.
To re-authenticate, please run:
az login
```

This only happens with the ADFS identity system.

This worked fine with version 2.29

**To Reproduce**
Run this command:

```
az login --tenant ' -u '' -p '' --service-principal -o table
```

**Expected behavior**
Azure CLI should log in correctly

**Environment summary**

- Azure CLI on windows using `.msi` and version 2.30.0
- Azure Stack Hub using ADFS
- hybrid profile `2020-09-01-hybrid`

**Additional context**

I can log in using powershell with the same service principal secret that fails with Azure CLI