net: TestTCPConcurrentAccept failures

[gopherbot]

#!watchflakes
default <- pkg == "net" && test == "TestTCPConcurrentAccept"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestTCPConcurrentAccept
    tcpsock_test.go:462: too many Dial failed: 12
--- FAIL: TestTCPConcurrentAccept (20.94s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "net" && test == "TestTCPConcurrentAccept"

2026-04-21 15:37 gotip-windows-amd64-race go@2fb2b98d net.TestTCPConcurrentAccept (log)

=== RUN   TestTCPConcurrentAccept
    tcpsock_test.go:462: too many Dial failed: 12
--- FAIL: TestTCPConcurrentAccept (20.94s)

— watchflakes

[prattmic]

cc @ianlancetaylor @neild @nicholashusin