enables retry on connection drop

[baywet]

Fixes #313

Changes proposed in this pull request

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[github-actions]

Conflicts have been resolved. A maintainer will take a look shortly.

[MIchaelMainer]

Do you always see a dropped connection + retry in the test?

https://github.com/microsoftgraph/msgraph-sdk-java/pull/473/files#diff-6709b7f7a4c3667aae557143946c5ab2R180

[baywet]

@MIchaelMainer this actually fixes 3 problems:

• Okhttp on jre11+ initiates the connection using HTTP/2 by default instead of http/1.1 for jre8. Our services for some reason send a connection reset when they see HTTP/2 coming. -> locks to http/1.1
• Our retry handler only retries on receiving responses (429, 504,...) but it doesn't retry on connection drop/reset etc (for some reason AGS sends a connection reset when it gets hot). -> enables retry connection from the http lib.
• Our retry handler was never integration tested -> adds a integration test that tests heavy load working. (which also allowed me to debug the other two cases)

[yschimke]

It's worth testing this again with HTTP/2 with OkHttp 4.10.0-RC1

https://square.github.io/okhttp/changelog/#version-4100-rc1

Fix: Attempt to read the response body even if the server canceled the request. This will cause some calls to return nice error codes like HTTP/1.1 429 Too Many Requests instead of transport errors like SocketException: Connection reset and StreamResetException: stream was reset: CANCEL.

[baywet]

Hey @yschimke
Thanks for letting us know! I logged #554 as we plan to upgrade ok http with that version