Make config framework able to reload module configs with multiple config files.

Make config framework able to reload module configs with multiple config files.

The config framework is supposed to be able to load configs that come from
multiple config files.  The principle example is chan_sip's sip.conf and
users.conf.  Unfortunately, it only does this correctly on initial load.
This patch causes the module's config to be reloaded entirely if any of
the config files change.

(closes issue ASTERISK-22009)
Reported by: Richard Mudgett

Review: https://reviewboard.asterisk.org/r/2859/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@399352 65c4cc65-6c06-0410-ace0-fbb531ad65f3