Sync latest log module from oslo-incubator

This commit syncs the latest version of the log module oslo-incubator.
Depends-On: Iee20319e7596232de5bed5b9755381ead44e3f46
Closes-Bug: #1386530
Change-Id: Ibc6fde39f93dd620f8e6020129aa7c10d12b581f
Merge "Sync latest log module from oslo-incubator"