testing: tests involving SIGINT handler fail with -test.v

[hyangah]

Since http://golang.org/cl/44352, a SIGINT handler is set up by testing framework when running tests with -v.
The handler reports in-progress tests upon SIGINT, and then re-raise SIGINT.
This can cause troubles when other SIGINT handlers exist.

Minimal repro case from @neild

func TestSignals(t *testing.T) {
	proc, err := os.FindProcess(os.Getpid())
	if err != nil {
		t.Fatal(err)
	}

	sigc := make(chan os.Signal, 1)
	signal.Notify(sigc, os.Interrupt)

	go func() {
		<-sigc
		signal.Stop(sigc)
	}()

	proc.Signal(os.Interrupt)
	time.Sleep(1 * time.Second)
}

$ go test -v
=== RUN   TestSignals
tests in progress: TestSignals
signal: interrupt
FAIL    _/usr/local/google/home/hakim/tmp/signal        0.020s

$ go test
PASS
ok      _/usr/local/google/home/hakim/tmp/signal        1.016s

This is confusing and affecting users.

@bcmills @ianlancetaylor

[ianlancetaylor]

Already fixed by CL 48370 which rolled back the patch installed to fix #19397. Closing this issue.