tests: Avoid another 'grep' in ps output

Previous fix at
----------------------------->
764c42813df3de9659a1ab7b7356779d2e5d64e5
<-----------------------------
Was incomplete

Change-Id: I6662168a7af078935a5cbcfae76ec40fc0c112b8
BUG: 887098
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/5672
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>