ovirt-live: remove output messages from dialog

Also other cleanups - synced centos/fedora engine-setup-yad.sh
scripts (hopefully will be merged one day)

Change-Id: Ic67adf2f03491578f70f0c226e2fa9f571a07490
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1056975
Signed-off-by: Ohad Basan <obasan@redhat.com>
Signed-off-by: Yedidyah Bar David <didi@redhat.com>