Keep the post transaction output clean from selinux output
I've noticed when installing katello rpms the following stdout:
restorecon reset /var/lib/crane/metadata context system_u:object_r:va
Since other commands usually don't produced anything to stdout in post section,
it looked suspicious. I think keeping it quiet would avoid some unnecessary
user panic during the installation.
(cherry picked from commit f29163c3b578c005532db739eb5da12f52750eeb)