tests: Adds mock patch autospec fixture

When mocking something, there's the possibility to reference a
property that does not exist, or call a method with invalid arguments,
but the unit tests to keep passing, resulting in false positives.

We've seen this issue several times in OpenStack, and we have created
and started using a mock patch fixture (can be seen in OpenStack Nova's test.py)
which enables autospec by default.

This guarantees 2 things: that the thing we're patching exists, and if it's
callable, that the calls respect the callable's signature (e.g.: no unknown
arguments can be used).

coriolis/tests/__init__.py

@@ -0,0 +1,10 @@
+# Copyright 2024 Cloudbase Solutions Srl
+# All Rights Reserved.
+
+from oslotest import mock_fixture
+
+# NOTE(claudiub): this needs to be called before any mock.patch calls are
+# being done, and especially before any other test classes load. This fixes
+# the mock.patch autospec issue:
+# https://github.com/testing-cabal/mock/issues/396
+mock_fixture.patch_mock_module()