Remove the unsafe bridge parameter from ast_bridge_hook_callback's.

Most hook callbacks did not need the bridge parameter.  The pointer value
could become invalid if the channel is moved to another bridge while it is
executing.

* Fixed some issues in feature_attended_transfer() as a result.

* Reduce the bridge inhibit count in
attended_transfer_properties_shutdown() after it has restored the bridge
channel hooks.

* Removed basic bridge requirement on feature_blind_transfer().  It does
not require the basic bridge like feature_attended_transfer().


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@395574 65c4cc65-6c06-0410-ace0-fbb531ad65f3