kamailio.cfg: replaced force_rtp_proxy()

- the function has been removed, replaced with rtpproxy_offer() and
  rtpproxy_offer()

etc/kamailio.cfg

@@ -754,7 +754,7 @@ route[RTPPROXY] {
 	if (is_method("BYE")) {
 		unforce_rtp_proxy();
 	} else if (is_method("INVITE")){
-		force_rtp_proxy();
+		rtpproxy_offer();
 	}
 	if (!has_totag()) add_rr_param(";nat=yes");
 #!endif
@@ -853,7 +853,7 @@ onreply_route[REPLY_ONE] {
 #!ifdef WITH_NAT
 	if ((isflagset(FLT_NATS) || isbflagset(FLB_NATB))
 			&& status=~"(183)|(2[0-9][0-9])") {
-		force_rtp_proxy();
+		rtpproxy_answer();
 	}
 	if (isbflagset("6")) {
 		fix_nated_contact();