Hyper-V: Refactors Hyper-V VMOps unit tests

The Hyper-V driver oldest tests (test_hypervapi.py) are proving hard to
maintain.

The tests in test_hypervapi.py in particular can also be refactored and
split in separate TestCases, one of each *ops module.

This commit refactors some unit tests from VMOps, necessary for the
next commits..

Partially implements: blueprint hyper-v-test-refactoring

Change-Id: I82a60c85d9d70b83c79d8cc031c2cd86813ea8d6
Merge "Hyper-V: Refactors Hyper-V VMOps unit tests"