Many HTTP requests on forge object creation

It looks to me like there are 19 connections [full log: 2] where 6 of them are duplicates [1]

Repro:

```
# turn on debug logging
import logging; logging.basicConfig(level=logging.DEBUG)

forge = KnowledgeGraphForge(
'https://raw.githubusercontent.com/BlueBrain/nexus-forge/master/examples/notebooks/use-cases/prod-forge-nexus.yml',
endpoint='https://bbp.epfl.ch/nexus/v1',
bucket='bbp/atlas',
token=token
)
```

[1] Duplicates:

| Requests | URL |
| ------- | --- |
| 2 | https://bbp.epfl.ch:443 "GET /nexus/v1/projects/bbp/atlas HTTP/1.1" 200 None |
| 2 | https://bbp.epfl.ch:443 "GET /nexus/v1/projects/neurosciencegraph/datamodels HTTP/1.1" 200 None |
| 2 | https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/atlas/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None |
| 2 | https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/neurosciencegraph/datamodels/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None |
| 3 | https://bbp.epfl.ch:443 "POST /nexus/v1/views/neurosciencegraph/datamodels/https%3A%2F%2Fbluebrain.github.io%2Fnexus%2Fvocabulary%2FdefaultSparqlIndex/sparql HTTP/1.1" 200 None |

[2] Full log:
```
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): raw.githubusercontent.com:443
DEBUG:urllib3.connectionpool:https://raw.githubusercontent.com:443 "GET /BlueBrain/nexus-forge/master/examples/notebooks/use-cases/prod-forge-nexus.yml HTTP/1.1" 200 642
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/projects/bbp/atlas HTTP/1.1" 200 None
DEBUG:charset_normalizer:Encoding detection: ascii is most likely the one.
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/atlas/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/projects/neurosciencegraph/datamodels HTTP/1.1" 200 None
DEBUG:charset_normalizer:Encoding detection: ascii is most likely the one.
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/neurosciencegraph/datamodels/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "POST /nexus/v1/views/neurosciencegraph/datamodels/https%3A%2F%2Fbluebrain.github.io%2Fnexus%2Fvocabulary%2FdefaultSparqlIndex/sparql HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "POST /nexus/v1/views/neurosciencegraph/datamodels/https%3A%2F%2Fbluebrain.github.io%2Fnexus%2Fvocabulary%2FdefaultSparqlIndex/sparql HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "POST /nexus/v1/views/neurosciencegraph/datamodels/https%3A%2F%2Fbluebrain.github.io%2Fnexus%2Fvocabulary%2FdefaultSparqlIndex/sparql HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/atlas/_/https%3A%2F%2Fbbp.neuroshapes.org HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/atlas/_/https%3A%2F%2Fneuroshapes.org HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): raw.githubusercontent.com:443
DEBUG:urllib3.connectionpool:https://raw.githubusercontent.com:443 "GET /BlueBrain/nexus-forge/master/examples/configurations/nexus-store/file-to-resource-mapping.hjson HTTP/1.1" 200 269
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/projects/bbp/atlas HTTP/1.1" 200 None
DEBUG:charset_normalizer:Encoding detection: ascii is most likely the one.
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/atlas/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): raw.githubusercontent.com:443
DEBUG:urllib3.connectionpool:https://raw.githubusercontent.com:443 "GET /BlueBrain/nexus-forge/master/examples/configurations/nexus-resolver/term-to-resource-mapping.hjson HTTP/1.1" 200 109
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/projects/neurosciencegraph/datamodels HTTP/1.1" 200 None
DEBUG:charset_normalizer:Encoding detection: ascii is most likely the one.
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/neurosciencegraph/datamodels/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): raw.githubusercontent.com:443
DEBUG:urllib3.connectionpool:https://raw.githubusercontent.com:443 "GET /BlueBrain/nexus-forge/master/examples/configurations/nexus-resolver/agent-to-resource-mapping.hjson HTTP/1.1" 200 75
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/projects/bbp/agents HTTP/1.1" 200 None
DEBUG:charset_normalizer:Encoding detection: ascii is most likely the one.
DEBUG:urllib3.connectionpool:Starting new HTTPS connection (1): bbp.epfl.ch:443
DEBUG:urllib3.connectionpool:https://bbp.epfl.ch:443 "GET /nexus/v1/resolvers/bbp/agents/_/https%3A%2F%2Fbluebrainnexus.io%2Fcontexts%2Fmetadata.json HTTP/1.1" 200 None
```

Edit: 6 instead of 7; note to self, `agents != atlas`