Adds admin_password as key to be sanitized when logging

The Nova V3 API is moving to use admin_password instead of
admin_pass (both are currently in use). So adding admin_password
as a key that the value should be sanitized for when
logging.

Change-Id: I0eb66c948516624db8b770498ae541025545d981
Partial-Bug: #1247217
Merge "Adds admin_password as key to be sanitized when logging"