Mask database user's password in trove logs

Currently passwords are logged in plaintext in trove-api and
trove-taskmanager logs. This fix will mask the passwords in the logs.
Syncing modules log, common.py from rpc  and versionutils from oslo.
common.py requires versionutils.py.

Change-Id:I50deb003d866e85e7c7ec8ab3ce7248d1c005e57
Closes-Bug: #1254914
Merge "Mask database user's password in trove logs"