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
Port virtual-interfaces plugin to v2.1(v3) API

Ports virtual-interfaces extension and adapts it to the
v2.1/v3 API framework. API behaviour is identical.

- unittest code modified to share testing with both v2/v2.1
- Adds expected error decorators for API methods

Partially implements blueprint v2-on-v3-api

Change-Id: Ic25ae83ecfaaa461b6ddd044e04af844d02dd6b7
Code cleanup: quota limit validation

In the quota limit validation, the conditional expressions are
difficult to understand because -1 which means an unlimited value is
compared directly.

By converting -1 to infinity, the validation can be implemented with
simple numeric comparisons. It makes code maintenance much easier.

Change-Id: I74650cba121734a14d31b76607adea004804c815
Imported Translations from Transifex

For more information about this automatic import see:
https://wiki.openstack.org/wiki/Translations/Infrastructure

Change-Id: I3823ea46b26b921642b373b1495ffb3a448f121f
Merge "Port virtual-interfaces plugin to v2.1(v3) API"
Merge "Code cleanup: quota limit validation"
Merge "Imported Translations from Transifex"
Merge "Hyper-V: Adds HostOps unit tests"