Drop dependency oslo.db from common.log

Openstack common.log module registers a few oslo.config options,
which possibly could cause of DuplicateOptError raising in case of use
of both common.log and oslo.db in target projects.
Thus logging module from python standart library should be used.

Change-Id: I1ab30ab99ec2564687ee166aa93aab32268e4c1d
Blueprint: oslo-db-lib
Merge "Drop dependency oslo.db from common.log"