test: fix http-upgrade-client flakiness

It's not guaranteed that the socket data is received in the same chunk
as the upgrade response. Listen for the `data` event to make sure all
the data is received.

PR-URL: #4602
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-http-upgrade-client.js

@@ -40,9 +40,14 @@ srv.listen(common.PORT, '127.0.0.1', function() {
  }
  });
  req.on('upgrade', function(res, socket, upgradeHead) {
- // XXX: This test isn't fantastic, as it assumes that the entire response
- // from the server will arrive in a single data callback
- assert.equal(upgradeHead, 'nurtzo');
+ var recvData = upgradeHead;
+ socket.on('data', function(d) {
+ recvData += d;
+ });
+
+ socket.on('close', common.mustCall(function() {
+ assert.equal(recvData, 'nurtzo');
+ }));
 
  console.log(res.headers);
  var expectedHeaders = {'hello': 'world',