etc/kamailio.cfg: define option to relay RTP always

- skip the NAT condition for RTP relaying, can be helpful for ALGs that
  fix the signaling but leave direct RTP streams blocked

etc/kamailio.cfg

@@ -53,6 +53,7 @@
 # *** To enable nat traversal execute:
 #     - define WITH_NAT
 #     - option for NAT SIP OPTIONS keepalives: WITH_NATSIPPING
+#     - option to relay RTP always (with RTPProxy or RTPEngine): WITH_RTPRELAY
 #     - install RTPProxy: http://www.rtpproxy.org
 #     - start RTPProxy:
 #        rtpproxy -l _your_public_ip_ -s udp:localhost:7722
@@ -897,7 +898,10 @@ route[NATMANAGE] {
 			}
 		}
 	}
+
+#!ifndef WITH_RTPRELAY
 	if (!(isflagset(FLT_NATS) || isbflagset(FLB_NATB))) return;
+#!endif
 
 #!ifdef WITH_RTPENGINE
 	if(nat_uac_test("8")) {