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/cmd_utils.py b/client/cros/audio/cmd_utils.py
index b739b68..d6423a1 100644
--- a/client/cros/audio/cmd_utils.py
+++ b/client/cros/audio/cmd_utils.py
@@ -12,6 +12,7 @@
 import subprocess
 import threading
 
+from subprocess import PIPE
 from autotest_lib.client.common_lib.utils import TEE_TO_LOGS
 
 _popen_lock = threading.Lock()