Drop ExclusiveArch

Vdsm supports ppc, and should be built for ppc also for el7.

Change-Id: If98acd4003a0b9311cfc0d502c86b2b18d55790c
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/31182
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Michal Skrivanek <michal.skrivanek@redhat.com>