HTTP/2 does not work with outbound transparent

[shinrich]

Once I fixed issue #7525, I could pass traffic for HTTP and HTTPS HTTP/1.1 with the certifier plugin. But for HTTP/2 traffic I would get a 500 response. Looking at the debug messages, it appeared that the HttpSM was very insistent about doing a DNS lookup on the domain.

Eventually tracked it down to the fact that the accept object transparent flags were not being propagated properly to the Http2Streams. I am putting up a PR that fixes the issue, but perhaps in not the most beautiful way.

This is observed working on the 9.1.1 codebase.

[shinrich]

After some more testing, my original fix only worked if http caching was enabled. There was a different path followed if caching was disabled. Centralized the fix a bit more to address both caching and non-caching cases. Getting ready to set up PR.

[shinrich]

Talked with @SolidWallOfCode about my original PR. He pointed out the proxy.config.http.use_client_target_addr setting which fixed quite a few things. Setting it to 2 made my environment work where the gateway didn't have the same DNS access as the client. I set up PR #8593 to clean up the documentation with obsolete info and highlighted this setting.

Changed the code PR #8594 to propagate the outbound settings to the HTTP/2 stream as they are being propagated to the HTTP1 client until we can get the session-based hook solution figured out.