packaging: setup: Add host rename script

Provide a script that does some of the work involved in changing
an engine's hostname. More details in:
http://www.ovirt.org/Changing_Engine_Hostname

Change-Id: I28cb0285424236fd3e6907694f6bf1ce6ce3367f
Signed-off-by: Yedidyah Bar David <didi@redhat.com>