NSX: properly handle floating ip status

Ensure the floating IP status is put ACTIVE or DOWN when it
is associated or disassociated.
This is done directly on the plugin class as the NSX backend
applies relevant NAT rules synchronously.

Change-Id: Ie747c4eae2ac33016fdabaade2335f7d2d24eec9
Closes-Bug: #1334708
VPNaaS REST Client UT Broken

When the H302 work was done, it broke two modules used for UT of
Cisco CSR VPNaaS REST client. Since the UT is currently disabled
(because the httmock library was not approved for test-requirements),
the error was not detected.

This fixes the files, so that they can still be used manually (by
locally importing httmock or its source file, and renaming the
module to remove the "_" prefix).

In the long term, the UT needs to be reworked to use httpretty,
which uses a register based mechanism, instead of a context
manager based mechanism, so this will take some effort. In addition.
there is discussion of switching to a new mock-request package,
instead of httpretty.

Change-Id: I8badc249ad021fdbdb2367b5416c72435ed58994
Closes-Bug: 1335977
Closes-Bug: 1326785
Merge "VPNaaS REST Client UT Broken"
Merge "NSX: properly handle floating ip status"