Adding rsyslog requierment to spec

Without rsyslog service, vdsm logger throws exception and does not
start.

Change-Id: Ia0efc1f55a9c97c71f31c1d0bdbcc0bbe3ea1db4
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=928861
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13509
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>