HTTP/2 Unit Test race condition

Motivation:
The Http2ConnectionRoundtripTest.noMoreStreamIdsShouldSendGoAway unit test had a race condition where it would sometimes receive a SETINGS_ACK message that was not anticipated. This caused the test to fail because of bad test code.

Modifications:
The bad unit test should be updated to handle the message exchange for a good connection setup, and then the GO_AWAY frame.

Result:
Http2ConnectionRoundtripTest.noMoreStreamIdsShouldSendGoAway should no longer sporadically fail.
HTTP/2 Draft 16

Motivation:
HTTP/2 draft 16 has been released https://tools.ietf.org/html/draft-ietf-httpbis-http2-16.

Modifications:
The HTTP/2 codec should be updated to support draft 16.

Result:
HTTP/2 codec is draft 16 compliant.