packaging: setup: allow automation for cluster

Allow automation for cluster selection.
Introduce a second answer file saving as last step of
closeup stage, storing the cluster name selected for
reusing it on additional hosts.

Change-Id: I699dda9d1286b8d6f2e251a5f0ffcaa43725da21
Related-To: http://bugzilla.redhat.com/1059950
Related-To: http://bugzilla.redhat.com/1043906
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>