ML2 UT: Fix incorrect mock return value

In the UT for ML2 Cisco Nexus MD,
in the function test_ncclient_version_detect()
The value being passed into the mock is incorrect
to mock the ncclient connect object.

Change-Id: Ife1fc2a8f8fe284605ad77cee4ffa307e6d5360c
Closes-Bug: #1404927
Merge "ML2 UT: Fix incorrect mock return value"