Configure logging format flexibly

Now we can get tempest log file with options in run_tests.sh.
This adds log.py and enables to configure log format more flexibly
using configuration file.
This adds a LoggerAdaptor and a Formatter to output each test name
to log lines.

Implements: blueprint add-logging-configuration

Change-Id: I88cf18bb8bbc152e62ac83a9c7dc26067b7a11bd
diff --git a/tempest/api/identity/__init__.py b/tempest/api/identity/__init__.py
index e5fdc1b..718aa15 100644
--- a/tempest/api/identity/__init__.py
+++ b/tempest/api/identity/__init__.py
@@ -15,7 +15,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import logging
+from tempest.common import log as logging
 
 LOG = logging.getLogger(__name__)