Password config options should be marked secret

Password config options should be marked secret

If passwords are not marked secret, there is the potential for
them to be logged in a world readable location.

Link to the OSSG guideline (may change in the future):
https://github.com/hyakuhei/OSSG-Security-Practices/blob/master/sensitive_config_file_options.md

Oslo.config descriptions:
http://docs.openstack.org/developer/oslo.config/cfg.html#special-handling-instructions

SecImpact

Change-Id: I6d5c80b7610d593fdd331c726039f1456d2c5bf7