Add <version> arg to keystone-manage db_sync

This optional <version> argument allows a client of db_sync to indicate to
which database version to upgrade or downgrade.

Change-Id: I3ccf45eb572a3897e5d3bc5bd17566493a55f393
Improve the performance of tokens deletion for user

Provide new delete the tokens api 'delete_tokens' to support
delete all the tokens for user in one session in the sql backend. For
the kvs and memcache, I also provide the corresponding implementation.

Fix bug 1178063

Change-Id: I986a583e5900ea04e26cbdb7c49638a33818bca7
Merge "Add <version> arg to keystone-manage db_sync"