Remove native bridging check for DTMF based transfers. Thanks to the last...

Remove native bridging check for DTMF based transfers. Thanks to the last batch of RTP changes it is no longer required for the media stream to go through Asterisk if DTMF is going over signalling. It will simply reinvite back as needed.
(closes issue #11172)
Reported by: ibc


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89057 65c4cc65-6c06-0410-ace0-fbb531ad65f3