* move set_module_args to units.modules.utils
* unit tests: reuse set_module_args
* unit tests: mock exit/fail_json in module.utils.ModuleTestCase
* unit tests: use module.utils.ModuleTestCase
* unit tests: fix 'import shadowed by loop variable'
Ok, so for openvswitch_db in particular we just return one command
but in the sake of consistency and code re-use, let's return a list
of "commands", even if it's just one.
Rather than passing a file to load fixture, build a matrix containing
the run_command side_effect per test.
This will allow more code-reuse for other ovs modules unit tests.
