mod_cloud_notify: Cleanup code and drop support for prosody 0.9 This removes some legacy stuff that was needed for prosody 0.9 We now use util.stanza:find instead of our own patched version to be more mainstream The unneeded module unloading code was removed, too

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.