fix(controller): correct ExternalIDs filter logic in diffPolicyRouteWithLogical

Cherry-pick of kubeovn#6577 accidentally inverted the isU2ORoutePolicy condition,
causing all existing policies with empty ExternalIDs to be skipped, leading
to spurious dels/adds on every reconcile.

Restore the correct filter: skip vpc-egress-gateway, subnet-owned, and
isU2ORoutePolicy routes (not user-defined policy routes).

Author: zbb88888

pkg/controller/vpc.go

@@ -1079,8 +1079,8 @@ func diffPolicyRouteWithLogical(exists []*ovnnb.LogicalRouterPolicy, target []*k
 	existsMap = make(map[string]*kubeovnv1.PolicyRoute, len(exists))
 
 	for _, item := range exists {
-		if item.ExternalIDs["vpc-egress-gateway"] != "" ||
-			item.ExternalIDs["isU2ORoutePolicy"] != "true" {
+		if item.ExternalIDs["vpc-egress-gateway"] != "" || item.ExternalIDs["subnet"] != "" ||
+			item.ExternalIDs["isU2ORoutePolicy"] == "true" {
 			continue
 		}
 		policy := &kubeovnv1.PolicyRoute{