tests: Run prove in UTC timezone

This will make it easy in finding the relevant logs easy.

Change-Id: I9ac9988327ea28c20477655df9c9f606fd7d6c8e
BUG: 1092850
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7810
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>