Rename/remove Nicira NVP references from VMware NSX unit tests

This patch sweeps for Nicira and NVP references and replace
them with VMware and NSX where possible. Some clean-up is
done along the way to improve the organization of the
unit tests module.

Partial-implements blueprint: nicira-plugin-renaming

Change-Id: I48e4779ccec64ba300b26d4967d3f9fae7cfdc14
Merge "Rename/remove Nicira NVP references from VMware NSX unit tests"