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.
........

Merged revisions 374085 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@374086 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -12226,6 +12226,7 @@ static void add_ice_to_sdp(struct ast_rtp_instance *instance, struct ast_str **a
 		}
 
 		ast_str_append(a_buf, 0, "\r\n");
+		ao2_ref(candidate, -1);
 	}
 
 	ao2_iterator_destroy(&i);