test: intermitent failures in test-cluster-worker-disconnect #1757

assert.js:88
  throw new assert.AssertionError({
        ^
AssertionError: Disconnect event did not emit
    at process.<anonymous> (/usr/home/sgimeno/node/io.js/test/parallel/test-cluster-worker-disconnect.js:84:12)
    at process.g (events.js:260:16)
    at emitOne (events.js:82:20)
    at process.emit (events.js:169:7)
    at process.exit (node.js:745:17)
    at /usr/home/sgimeno/node/io.js/test/parallel/test-cluster-worker-disconnect.js:74:15
    at doNTCallback0 (node.js:408:9)
    at process._tickCallback (node.js:337:13)