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/services/volume/xml/snapshots_client.py b/tempest/services/volume/xml/snapshots_client.py
index 2209fc7..410ed3e 100644
--- a/tempest/services/volume/xml/snapshots_client.py
+++ b/tempest/services/volume/xml/snapshots_client.py
@@ -12,12 +12,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import logging
 import time
 import urllib
 
 from lxml import etree
 
+from tempest.common import log as logging
 from tempest.common.rest_client import RestClientXML
 from tempest import exceptions
 from tempest.services.compute.xml.common import Document