Stasis: Allow internal channels directly into bridges

Stasis: Allow internal channels directly into bridges

The patch to catch channels being shoehorned into Stasis() via external
mechanisms also happens to catch Announcer and Recorder channels
because they aren't known to be stasis-controlled channels in the usual
sense. This marks those channels as Stasis()-internal channels and
allows them directly into bridges.

Review: https://reviewboard.asterisk.org/r/3903/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@420795 65c4cc65-6c06-0410-ace0-fbb531ad65f3