Fix logging on the prepare stage

When test fails on the prepare fixture stage
the logs capturing is not working
Patch adds snapshot fixture call to the
prepare function

Closes-Bug:1669369

Change-Id: Icb280957ef2801acea48394acc432e56b835e97a

fuel_tests/tests/conftest.py

@@ -97,7 +97,7 @@ def snapshot(request):
 
 
 @pytest.fixture(scope='function', autouse=True)
-def prepare(request):
+def prepare(request, snapshot):
     """Fixture for prepearing environment for test.
 
     Provided two marker behaviour: