x/net/http2: server sends RST_STREAM w/ PROTOCOL_ERROR to clients it incorrectly believes have violated max advertised num streams [1.16 backport]

[gopherbot]

@neild requested issue #42777 to be considered for backport to the next 1.16 minor release.

@gopherbot please open backport issues for 1.16 and 1.17.

[gopherbot]

Change https://golang.org/cl/346889 mentions this issue: [internal-branch.go1.16-vendor] http2: complete outstanding async write before reading the next frame

[gopherbot]

Change https://golang.org/cl/347031 mentions this issue: [release-branch.go1.16] all: update golang.org/x/net to pull in CL 346890

[gopherbot]

Closed by merging 8226cb0 to release-branch.go1.16.