spec: Require qemu-kvm-rhev in EL

In EL qemu-kvm does not support live snapshots. In order to support
them, qemu-kvm-rhev is required. This package is now available in the
ovirt-releases repository [1].

[1] http://www.ovirt.org/Vdsm_Developers

Change-Id: Iae9ad6599a79bec94365b952fc09cfaf75fe0628
Bug-Url: https://bugzilla.redhat.com/1127763
Signed-off-by: Allon Mureinik <amureini@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/31214
Reviewed-by: Sandro Bonazzola <sbonazzo@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>