NSX: get rid of the last Nicira/NVP bits

These were kept for bw compatibility in Icehouse, but
these are removed in Juno.

The king is dead, long live the king!

DocImpact
Blueprint: nicira-plugin-renaming

Change-Id: I49d19fec90ba191ed5b895fac8a884070f52119e
Merge "NSX: get rid of the last Nicira/NVP bits"