add cflags from contact to branch flags

* sets nat flags if device is registered
  and kazoo invite format is not contact

kamailio/default.cfg

@@ -865,6 +865,7 @@ route[ROUTE_TO_AOR]
     } else if (reg_fetch_contacts("location", "$hdr(X-KAZOO-AOR)", "callee")) {
        $du = $(ulc(callee=>received));
        $fs = $(ulc(callee=>socket));
+       $bf = $bf | $(ulc(callee=>cflags));
        xlog("L_INFO", "$ci|log|routing $hdr(X-KAZOO-AOR) to $du via $fs\n");
        $avp(aor) = $hdr(X-KAZOO-AOR);
     } else {