net: TestDialerDualStackFDLeak failures

[gopherbot]

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

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestDialerDualStackFDLeak
    dial_test.go:131: got 1; want 0
--- FAIL: TestDialerDualStackFDLeak (0.31s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

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

2025-09-09 19:10 gotip-netbsd-arm64 go@4c63d798 net.TestDialerDualStackFDLeak (log)

=== RUN   TestDialerDualStackFDLeak
    dial_test.go:131: got 1; want 0
--- FAIL: TestDialerDualStackFDLeak (0.31s)

— watchflakes