rtpengine: prevent from reversing tags on DELETE

When a delete is used on a reply route, do not reverse the tags,
otherwise rtpengine will not match the proper session. More details on
github, ticket #1339.

modules/rtpengine/rtpengine.c

@@ -1798,6 +1798,7 @@ static bencode_item_t *rtpe_function_call(bencode_buffer_t *bencbuf, struct sip_
 	bencode_list_add_string(item, ip_addr2a(&msg->rcv.src_ip));
 
 	if ((msg->first_line.type == SIP_REQUEST && op != OP_ANSWER)
+		|| (msg->first_line.type == SIP_REPLY && op == OP_DELETE)
 		|| (msg->first_line.type == SIP_REPLY && op == OP_ANSWER))
 	{
 		bencode_dictionary_add_str(ng_flags.dict, "from-tag", &from_tag);