testing: roll back CL 44352 (show in-progress tests upon SIGINT)

CL 44352 changed the behavior of SIGINT, which can break tests that
themselves use SIGINT.  I think we can only implement this if the
testing package has a way to know whether the code under test is using
SIGINT, but os/signal does not provide an API for that.  Roll back for
1.9 and think about this again for 1.10.

Updates #19397

Change-Id: I021c314db2b9d0a80d0088b120a6ade685459990
Reviewed-on: https://go-review.googlesource.com/48370
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/os/signal/signal_test.go b/src/os/signal/signal_test.go
index 6cf05f5..dea2add 100644
--- a/src/os/signal/signal_test.go
+++ b/src/os/signal/signal_test.go
@@ -4,7 +4,7 @@
 
 // +build darwin dragonfly freebsd linux netbsd openbsd solaris
 
-package signal_test
+package signal
 
 import (
 	"bytes"
@@ -14,7 +14,6 @@
 	"io/ioutil"
 	"os"
 	"os/exec"
-	. "os/signal"
 	"runtime"
 	"strconv"
 	"sync"