Restore and fix vmware unit tests

Restore and fix vmware unit tests

This patch actually restores vmware unit tests, by adding back
the __init__.py file which was renamed during the advanced
service spinoff and not reinstated when fixing vmware code to
comply with the spinoff.

Furthermore, this patch also fixes a minor issue with context
usage in vmware unit tests which is triggering failures because
of the new database constraint introduced with the commit
79c97120de9cff4d0992b5d41ff4bbf05e890f89

Finally, flake8 tests on vmware directories are also restored
with this patch.

Change-Id: Ib63463fca28bbb4a1eb60b8f5f4b63b3d3367c9e
Closes-Bug: #1416593
Closes-Bug: #1416596