net: skip TestVariousDeadlines on Plan 9

This test is regularly failing on the plan9/386
builder running on GCE, but we haven't figured
out the issue yet.

Updates #26945.

Change-Id: I8cbe0df43c0757e7bc68e370311f4a28cd7b049b
Reviewed-on: https://go-review.googlesource.com/c/152721
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/timeout_test.go

@@ -812,6 +812,9 @@ func (b neverEnding) Read(p []byte) (int, error) {
 }
 
 func testVariousDeadlines(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test on plan9; see golang.org/issue/26945")
+	}
 	type result struct {
 		n   int64
 		err error