apps/app_meetme: Apply default values on initial load with no config file

When the app_meetme module is loaded without its configuration file, the
module settings aren't initialized. In particular, this impacts the use
of logging realtime members. This patch guarantees that we always set the
default module settings on initial load.

Review: https://reviewboard.asterisk.org/r/4242/

ASTERISK-24572 #close
Reported by: Nuno Borges
patches:
  24572.patch uploaded by Nuno Borges (License 6116)
........

Merged revisions 429027 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@429028 f38db490-d61c-443f-a65b-d21fe96a405b