fix java build failure (#6062)

java/runtime/src/main/resources/ray.default.conf

@@ -84,6 +84,8 @@ ray {
   raylet {
     // RPC socket name of Raylet
     socket-name: /tmp/ray/sockets/raylet
+    // Listening port for node manager.
+    node-manager-port: 0
 
     // See src/ray/ray_config_def.h for options.
     config {