Fetch Discovery Document doesn't support retry mechanism

[mik-laj]

The library currently supports retrying requests when an external API operation is performed.
https://github.com/googleapis/google-api-python-client/blob/master/googleapiclient/http.py#L967-L977
https://github.com/googleapis/google-api-python-client/blob/master/googleapiclient/http.py#L172
However, this does not happen when sending the first request to the Discovery API.
https://github.com/googleapis/google-api-python-client/blob/master/googleapiclient/discovery.py#L282

Environment details

• OS: Linux/MacOS
• Python version: All
• pip version: All
• google-api-python-client version: google-api-python-client

Steps to reproduce

1. Create any service object
2. If a connection problem occurs, the request will not be retried