Hyper-V: Adds HostOps 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 the HostOps test cases.

Co-Authored-By: Robert Tingirica <rtingirica@cloudbasesolutions.com>

Partially implements: blueprint hyper-v-test-refactoring

Change-Id: I2f20401ed8c01c08d2fecab9356b70ee58b3e8fa
Merge "Hyper-V: Adds HostOps unit tests"