cmd_utils - Import PIPE to this namespace

So users don't need to import subprocess again just for PIPE.

TEST=Run related tests on link
BUG=None

Change-Id: Id891dda00eb0c6d208d7390b1bb6534a61374b12
Reviewed-on: https://chromium-review.googlesource.com/180392
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
Commit-Queue: Owen Lin <owenlin@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
diff --git a/client/cros/audio/alsa_utils.py b/client/cros/audio/alsa_utils.py
index 9281ca7..57e81d2 100644
--- a/client/cros/audio/alsa_utils.py
+++ b/client/cros/audio/alsa_utils.py
@@ -3,7 +3,6 @@
 # found in the LICENSE file.
 
 import shlex
-import subprocess
 
 from autotest_lib.client.cros.audio import cmd_utils
 
@@ -100,7 +99,7 @@
     cmd = 'amixer -c %d scontrols'
     id = 0
     while True:
-        p = cmd_utils.popen(shlex.split(cmd % id), stdout=subprocess.PIPE)
+        p = cmd_utils.popen(shlex.split(cmd % id), stdout=cmd_utils.PIPE)
         output, _ = p.communicate()
         if p.wait() != 0: # end of the card list
             break;
@@ -115,4 +114,4 @@
     if device is None:
         device = 'hw:%d' % get_default_soundcard_id()
     args = [AMIXER_PATH, '-D', device, 'contents']
-    return cmd_utils.execute(args, stdout=subprocess.PIPE)
+    return cmd_utils.execute(args, stdout=cmd_utils.PIPE)