Simplify test_suite().
* bzrlib/tests/test_selftest.py:
(TestTestIdList.test_test_suite): Updated to reflect new module
order in the list.
* bzrlib/tests/__init__.py:
(packages_to_test): Deleted. The list is empty now.
(test_suite): Simplified, all tests modules can now be loaded with
loadTestsFromModuleName.