This commit finishes and fixes the integration of xivo_test_helpers
AssetLaunchingTestCase for base confd integration tests.

tl;dr:
- use a fake test in test_aa_start_asset_for_all_tests file to start the
  asset via BaseIntegrationTestStart class
- use a fake test in test_zz_stop_asset_for_call_tests file to stop the
  asset via BasetIntegrationTestStop class

Longer explanation:
- By moving towards unittest we had to put all test function in TestCase
  subclass.
- There is no setup/teardown function at the suite level in unittest.
- We wanted to keep the start asset -> test all base -> stop asset
  execution that nosetest was doing
- We "faked" that with this test_aa and test_zz files based on the
  way unittest loads test

Idea for future:
- create our own test runner
- or implement a mechanism in the class that start only the asset if not
  already started