修复DNS逻辑错误的问题

route/route.go

@@ -792,9 +792,15 @@ func (r *Router) actionResolve(ctx context.Context, metadata *adapter.InboundCon
 	if metadata.Destination.IsDomain() {
 		var transport adapter.DNSTransport
 		if action.Server != "" {
-			var loaded bool
-			transport, loaded = r.dnsTransport.Transport(action.Server)
+			var (
+				loaded    bool
+				ambiguous bool
+			)
+			transport, loaded, ambiguous = adapter.LookupDNSTransport(r.dnsTransport, action.Server)
 			if !loaded {
+				if ambiguous {
+					return E.New("DNS server is ambiguous: ", action.Server)
+				}
 				return E.New("DNS server not found: ", action.Server)
 			}
 		}