mod_sofia Gateway Ping needs to look for return code 501 (SFSIP-78)

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@9243 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/endpoints/mod_sofia/sofia.c

@@ -1929,7 +1929,7 @@ static void sofia_handle_sip_r_options(switch_core_session_t *session, int statu
 	}
 
 	if (gateway) {
-		if (status == 200 || status == 404) {
+		if (status == 200 || status == 404 || status == 501) {
 			if (gateway->state == REG_STATE_FAILED) {
 				gateway->state = REG_STATE_UNREGED;
 				gateway->retry = 0;