This test uses method (*UDPConn).WriteMsgUDPAddrPort, which is
not supported on Plan 9. The test needs to be skipped, like
for example TestAllocs which is already skipped for the
same reason.
Fixes #75017
Change-Id: Iaa0e6ecdba0938736d8f675fcac43c46db34cb5d
Reviewed-on: https://go-review.googlesource.com/c/go/+/696095
Auto-Submit: Damien Neil <dneil@google.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>