Move JSON filter unit tests into own file

Separates JSON filter unit tests from test_host_filters.py and refactors
the test methods to remove some cruft.

Change-Id: I31b9b409f4bbc17074067f42ea9da1418d963086
Separate filter unit tests for agg extra specs

This patch separates the unit tests for the aggregate instance extra
specs filters out from test_host_filters.py. In the process, it converts
the unit tests to NoDBTestCase and mocks out any database calls.

Change-Id: I7b9f186052825667b585674491d0ddf6b566f8de
Moves trusted filter unit tests into own file

Breaks out trusted filter unit tests into their own file. In the
process, we remove all DB accesses from the unit tests and uncruft the
unit tests with mock.

Change-Id: Ic895b06a9f6a224f153f12ca5ab54dc8be931f13
Reduce the complexity of _get_guest_config()

Running flake8 to check for cyclomatic complexity showed that the
libvirt driver's _get_guest_config() method was the worst offender,
with a complexity of 67. This commit simply refactors this method,
splitting off nested cases into their own methods, and reduces the
complextity to 40. No functional changes are included.

Change-Id: Ic27e091f922118edb48b233fb31c702d9528bb75
Merge "Move JSON filter unit tests into own file"
Merge "Separate filter unit tests for agg extra specs"
Merge "Reduce the complexity of _get_guest_config()"
Merge "Moves trusted filter unit tests into own file"