Unit test for receive failure after timeout
Updated invalid client id test to check empty "" client id
Merge branch 'master' of https://github.com/dhirajsb/mqtt-client into dhirajsb-master

* 'master' of https://github.com/dhirajsb/mqtt-client:
  Updated invalid client id test to check empty "" client id
  Unit test for receive failure after timeout
Fixes the test failures that Dhiraj identified.