test: add dgram.Socket.prototype.bind's test

bind: https://github.com/nodejs/node/blob/master/lib/dgram.js#L140

Author: hiroppy

test/parallel/test-dgram-bind.js

@@ -1,13 +1,17 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const dgram = require('dgram');
 
 const socket = dgram.createSocket('udp4');
 
-socket.on('listening', function() {
+socket.on('listening', common.mustCall(() => {
+  assert.throws(() => {
+    socket.bind();
+  }, /^Error: Socket is already bound$/);
+
   socket.close();
-});
+}));
 
 const result = socket.bind(); // should not throw