mod_client_management: Use grant id from key This is a minor tweak - it's faster and preserves compatibility with older data formats (that we don't necessarily want to be compatible with, but some of us have messy data stores and it pays to be a little more robust).

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.