Tools for monitoring a message bus

...with the intention of triggering an immediate compose.

Overview: rpm-ostree-build-monitor connects to a qpid
message bus, listening for a user-specified (via .ini file)
event, and triggering a (user-specified) command. Since
the message bus in question requires Kerberos authentication,
a helper script runs via systemd timer and keeps a krb5cc
cache file topped up.