net/http: don't reuse connections that are experiencing errors [1.19 backport]

[gopherbot]

@ianlancetaylor requested issue #59690 to be considered for backport to the next 1.19 minor release.

@gopherbot Please open backport to 1.19.

Rationale quoting #60301 (which is for the other open minor release):

When encountered, this is a serious issue: requests are blocked until the kernel gives up on the socket (with default settings on a Linux host, that's around 17 minutes). If the operator restarts the application as a result, data loss may occur.

Although the fix is in x/net v0.10.0 it will not be available to most developers who likely import net/http (and so rely on the h2 bundle rolled into Go's releases)

The only viable workaround is to disable the H2 client entirely via environment variable.

[ianlancetaylor]

CC @neild

[dmitshur]

The upstream issue isn't resolved yet, and the Go 1.19 release has exited its support window per https://go.dev/doc/devel/release#policy. We happen to be doing an off-cycle release, but it's for #61197 and a few other compatibility-increasing fixes that were ready, and this one isn't.