Please review the unit test for MQTT

Author: bilna <bilnap@am.amrita.edu>
Author: Bilna P <bilna.p@gmail.com>

Closes #3844 from Bilna/master and squashes the following commits:

acea3a3 [bilna] Adding dependency with scope test
28681fa [bilna] Merge remote-tracking branch 'upstream/master'
fac3904 [bilna] Correction in Indentation and coding style
ed9db4c [bilna] Merge remote-tracking branch 'upstream/master'
4b34ee7 [Bilna P] Update MQTTStreamSuite.scala
04503cf [bilna] Added embedded broker service for mqtt test
89d804e [bilna] Merge remote-tracking branch 'upstream/master'
fc8eb28 [bilna] Merge remote-tracking branch 'upstream/master'
4b58094 [Bilna P] Update MQTTStreamSuite.scala
b1ac4ad [bilna] Added BeforeAndAfter
5f6bfd2 [bilna] Added BeforeAndAfter
e8b6623 [Bilna P] Update MQTTStreamSuite.scala
5ca6691 [Bilna P] Update MQTTStreamSuite.scala
8616495 [bilna] [SPARK-4631] unit test for MQTT