test: add coverage for string array dgram send()

This commit adds code coverage for dgram's Socket#send() where
the data is an array of strings.

PR-URL: nodejs#11247
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

test/parallel/test-dgram-send-multi-string-array.js

@@ -0,0 +1,13 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const dgram = require('dgram');
+const socket = dgram.createSocket('udp4');
+const data = ['foo', 'bar', 'baz'];
+
+socket.on('message', common.mustCall((msg, rinfo) => {
+  socket.close();
+  assert.deepStrictEqual(msg.toString(), data.join(''));
+}));
+
+socket.bind(() => socket.send(data, socket.address().port, 'localhost'));