packaging: spec: ovirt-engine-setup should pull engine plugin

to keep backward compatibility with older methods, ovirt-engine-setup is
engine specific and should pull the engine plugin explicitly.

the setup common is renamed to setup-base.

Change-Id: I95b0fd30ecc5024c082ba4649b6a08550edd46e9
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>