Fix CI on Node 7.7.2

[bajtos]

Description

Add workaround for what seems to be a Node 7.7.2 regression: net.createConnection(port) is failing with the following error, see e.g. https://travis-ci.org/strongloop/loopback/jobs/209262349:

  1) loopback application pauses request stream during authentication:
     Uncaught TypeError: "listener" argument must be a function
    at Socket.connect (net.js:943:10)
    at Socket.connect (node_modules/async-listener/index.js:76:27)
    at Object.exports.connect.exports.createConnection (net.js:76:35)
    at sendHttpRequestInOnePacket (test/integration.test.js:77:24)
    at Server.<anonymous> (test/integration.test.js:19:7)
    at emitListeningNT (net.js:1302:10)
    at node_modules/async-listener/glue.js:188:31
    at _combinedTickCallback (internal/process/next_tick.js:77:11)
    at process._tickDomainCallback [as _tickCallback] (internal/process/next_tick.js:128:9)

The same code passes on Node 7.7.1, see e.g. https://travis-ci.org/strongloop/loopback/jobs/209009746.

My proposed workaround is to explicitly pass a no-op callback argument:

net.createConnection(port, ()=>{});

Strangely enough, the problem CANNOT be reproduced when the failing test is run in isolation via mocha test/integration.test.js. To reproduce it, one has to add few more tests making HTTP requests, e.g. via

$ mocha -R dot test/access-control.integration.js test/integration.test.js

From looking at recent Node.js changes, it seems the problem was introduced by nodejs/node@b56e851 from nodejs/node#11667.

@joyeecheung @mcollina @jasnell you have authored/reviewed that patch, do you happen to have any insights on what may be wrong here?

cc @sam-github

[joyeecheung]

It is indeed a regression from Node's side. Should be fixed by nodejs/node#11762

[bajtos]

@joyeecheung lovely, thank you for chiming in and pointing us to the pull request fixing the regression. 👍 ❤️

In this light, I will rework my pull request to simply lock Travis CI config to 7.7.1 until a fixed version of Node.js is available.

[superkhau]

LGTM

[italoacasas]

https://nodejs.org/en/blog/release/v7.7.3/

[bajtos]

@italoacasas thanks! I opened a pull request to revert our Travis CI config back - #3285