Using pidStat to get pid creation time

In proc/pid/stat field 21(starttime) defined the time when the process
started. Before we used ctime (time of last status change) that might change
during process run.

Change-Id: Ie8e056472e5c83104168e55a8dd01a941a2357f3
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=966133
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/14998
Reviewed-by: Saggi Mizrahi <smizrahi@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>