tests: make sure to avoid 'grep' in ps output

Change-Id: I48909facd2e3a2dc52a18e44d58c0e0fa2d96ec3
BUG: 887098
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/5631
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>