Enabled Cisco ML2 driver to use new upstream ncclient

The code is still able to handle the old, custom ncclient that
we used before. It uses the different function signatures
for the ncclient's connect() function to detect which version
is installed.

Change-Id: I09d81b424d86f4cd35ca048507f06471246b91d8
Closes-Bug: 1352635
Removes extra indents from TestSubresourcePlugin

Removed extra indents from in front of each function in the
TestSubresourcePlugin class in test_api_v2.py so that it
meets pep8 requirements and matches up with the rest of the code.

Change-Id: Id194514d47508f8915aca18347a3c404b91a7abd
Closes-Bug: 1355100
Merge "Enabled Cisco ML2 driver to use new upstream ncclient"