Fix ref leak when adding ICE candidates to an SDP

There was a missing decrement to the reference count for the current ICE
candidate when local candidates are being added to an outbound SDP.  This
patch corrects that.



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@374085 65c4cc65-6c06-0410-ace0-fbb531ad65f3