Rewrite isOvirt function

Change-Id: I943594e8d2cb741f5400c8036b5af9f52ec13b38
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/16616
Reviewed-by: Dan Kenigsberg <danken@redhat.com>