Fix a bug where the DTMF mode was not set on newly created RTP instances in...

Fix a bug where the DTMF mode was not set on newly created RTP instances in the res_sip_sdp_rtp module.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@389568 65c4cc65-6c06-0410-ace0-fbb531ad65f3