mgr: omit module list in beacon logging

mgr: omit module list in beacon logging

This is useful in itself, but awkward when dealing
with logs generally, because it means that when you
grep on the name of a module, you get mostly beacon
messages rather than the log messages from the
module.

Signed-off-by: John Spray <john.spray@redhat.com>
(cherry picked from commit 8d1277fa5c578ce0ea23a70cc58c6cf99921ee25)