[fix] h2 double complete

[TingDaoK]

Issue #, if available:

Description of changes:

• In the case where the the remote sends GOAWAY marks the stream to be half closed, we will try to mark the stream complete, since we get a GOAWAY
• Meanwhile, if user also want to cancel the stream and sending a RST_STREAM. Nothing prevents this, and spec also allows RST_STREAM to be sent after receiving GOAWAY. However, with sending RST_STREAM, we also try to mark the stream complete. And in which case, we complete the stream twice and everything blows up.
• Add a simple boolean to prevent it from happening.

Arguably, we can prevent the RST_STREAM from a various places (User invoke, running the cross thread task ,etc..) But, sending it is not the real problem, and we do protect a lot around those when the connection/stream is shutting down. So, I chose to prevent the complete to happen again, so, every place can safely try to complete the stream regardless if it's already completed or not.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.68%. Comparing base (0409bc1) to head (618f5d8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #558   +/-   ##
=======================================
  Coverage   79.68%   79.68%           
=======================================
  Files          28       28           
  Lines       12082    12085    +3     
=======================================
+ Hits         9627     9630    +3     
  Misses       2455     2455           

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[azkrishpy]

should we mention this magic number?

[TingDaoK]

it's a comment in the test, so pretty much for ourselves to reference.