packaging: setup: Make pki interaction easier

Make pki interaction use files and ask again if needed.

Requires: http://gerrit.ovirt.org/32742

Bug-Url: https://bugzilla.redhat.com/1118328
Bug-Url: https://bugzilla.redhat.com/1118330
Change-Id: Ia5b3713330d6e11bd7c374e04f17660be79f2251
Signed-off-by: Yedidyah Bar David <didi@redhat.com>