Merge pull request #370 from vedujoshi/master

Add a knob in sanity_params to verify_on_setup=True/False so that fixtur...
changes for > 2 control nodes.Control nodes will now be calculated from discovery instead from testbed.py
Incorporated review comments
Merge pull request #377 from sandip-d/master

Incorpoarted review comments
Add skip test if MX is not available
Merge pull request #378 from chhandakm/master

Add skip test if MX is not available
Add check for default SG on a custom project