app_meetme: Fix overwrite of DAHDI conference data structure.

app_meetme: Fix overwrite of DAHDI conference data structure.

Starting a conference recording using the admin menu overwrites the DAHDI
conference data structure used to modify the admin user's conference mute
mode.

* Made no longer pass the user's DAHDI conference data structure into the
menu functions.  The menu now uses its own DAHDI conference data
structure to start the recording channel.

* Moved the unlock conf->playlock to before playing the conf-full message.
No sense keeping the lock while that prompt is playing.  The user is never
going to get into the conference at that point.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@413991 65c4cc65-6c06-0410-ace0-fbb531ad65f3