keystone: use keystone::cron::token_flush
keystone: use keystone::cron::token_flush

Instead of manually creating the crontab, use
keystone::cron::token_flush so we can leverage this code to
puppet-keystone.
This will have the same behavior, but will also store the logs in the
/var/log/keystone/keystone-tokenflush.log file.

Change-Id: Idee68597db64479bcbfbabe7b9697658a410d16b

mahak/packstack,mahak/packstack,mahak/packstack,xbezdick/packstack,openstack/packstack,openstack/packstack,stackforge/packstack,fr34k8/packstack,stackforge/packstack,openstack/packstack,imcsk8/packstack,fr34k8/packstack,fr34k8/packstack,imcsk8/packstack,stackforge/packstack,xbezdick/packstack,imcsk8/packstack,xbezdick/packstack