Use olso.log directly

As the openstack/common is deprecated, Watcher should use oslo lib
directly to run in the openstack env. So there is much work to do
with oslo. This patch fixed the log part.

Change-Id: I3145a842fe3a22b3d08fec60d180329073edd50f

watcher/common/messaging/events/event_dispatcher.py

@@ -14,9 +14,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from oslo_log import log
 
 from watcher.decision_engine.framework.messaging.events import Events
-from watcher.openstack.common import log
 
 LOG = log.getLogger(__name__)