VPNaaS REST Client UT Broken

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