x/net/http2: TestServer failures with "write: broken pipe" on openbsd

[bcmills]

--- FAIL: TestServer (10.64s)
    server_test.go:349: Error writing initial SETTINGS frame from client to server: write tcp 127.0.0.1:21462->127.0.0.1:34837: write: broken pipe
    server_test.go:267: Framer write log:
        2022-04-07 10:25:48.715770953 Framer 0xc001405500: wrote SETTINGS len=0
FAIL
FAIL	golang.org/x/net/http2	282.655s

greplogs --dashboard -md -l -e 'FAIL: TestServer .*(?:\n .*)*write: broken pipe'

2022-04-06T20:46:47-749bd19-81ae993/openbsd-mips64-jsing
2022-04-06T03:13:34-749bd19-5bb2628/openbsd-mips64-jsing
2022-02-08T15:30:12-cd36cc0-ef06a5f/openbsd-mips64-jsing
2021-09-12T16:46:58-a5e0955-ad97d20/openbsd-arm64-jsing

(attn @4a6f656c; CC @neild)

Since this only appears to affect certain OpenBSD builders, I plan to add a test skip and not follow up further.

[gopherbot]

Change https://go.dev/cl/398794 mentions this issue: http2: skip "write: broken pipe" failures in TestServer on OpenBSD