Always use the SQL backend for tokens.

The KVS has a number of drawbacks:

* Requires load balancer to persist connections to a single keystone
 server by token
* Memory will grow out of control until keystone server is restarted
*  At some point kvs lookups get very slow because there are millions of
*  keys in the dict.
* Process restart invalidates all tokens.

see e.g. https://bugs.launchpad.net/tripleo/+bug/1188301
Merge pull request #116 from dirkmueller/release/pebbles/master

Always use the SQL backend for tokens.
Merge pull request #118 from jtwill98/pull-req-release-roxy-master-17620546f850dd64dddb20c9c812824cc5589804

Merge of Latest Pebble commits into Roxy [12/13]