libvirt: split firewall tests out into test_firewall.py

The test_driver.py test module had a couple of classes which
were testing functionality from firewall.py. Since test_driver.py
is a really huge file, it is better for the firewall class tests
to live in a separate test_firewall.py module

Related-bug: #1369516
Change-Id: Ibb347780b7b79521ce87b08023771381726b0d53
libvirt: convert HostStateTestCase to avoid DB usage

The HostStateTestCase test case does not do anything DB
related. Convert it to NoDBTestCase to avoid DB setup penalty.
This improves perf from 1.7s to 0.2s

Partial-bug: #1369516
Change-Id: I0b1030b8a4e8c32f24c5b3a08ff86fa5bad06937
Merge "libvirt: split firewall tests out into test_firewall.py"
Merge "libvirt: convert HostStateTestCase to avoid DB usage"