KAZOO-532: remap 6XX to 4XX so we can send errors that are normally retried

opensips/opensips.tmp

@@ -944,6 +944,12 @@ failure_route[internal_fault]
 
         exit();
     }
+    else if (t_check_status("6[0-9][0-9]"))
+    {
+       send_reply("4$(T_reply_code{s.substr,1,0})", "$(<reply>rr)");
+
+       exit();
+    }
     else if (t_check_status("(4[0-9][0-9])|(5[0-9][0-9])"))
     {
         xlog("L_INFO", "$ci|start|received failure reply $T_reply_code $rr");