Increase verbose level for not found tempest tests

This warning prints old tempest tests (which are marked
as aliases in the guidelines) most of the time.
The warning confuses users becuase it may suggest that
a relevant test is missing, however, that's not the case,
aliases aren't supposed to be found because they were
renamed.

Therefore this commit increases the verbose level needed
to trigger these warnings. From now on, the warnings won't
be printed by default, debug level of verbosity will be
required.

Change-Id: Ic0e590d54d76e2d5839ced3f513e8b2ded705e6f

refstack_client/list_parser.py

@@ -147,7 +147,7 @@ class TestListParser(object):
                 else:
                     test_list.append(test_id + attr)
             except KeyError:
-                self.logger.warning("Test %s not found in Tempest list." %
+                self.logger.debug("Test %s not found in Tempest list." %
                                   test_id)
         self.logger.debug("Number of tests: " + str(len(test_list)))
         return test_list