Backwards compatibility with ubuntu-precise

Ubuntu precise has an older version of python-redis, so a number
of features used in keystone-redis upstream don't work. This
change does a few things:

* Removed redismw support, so it's not possible to write to
  multiple redis servers anymore.
* Changed StrictRedis to Redis, and fixed calls to the object for
  Redis class differences
* Added password support to the config and the connection pool