The token flush and token rotate crontabs are re-written when the
leader unit changes inline with Juju leadership management.

Align contexts used to generate crontabs with Juju leadership
status, rather than corosync/pacemaker.

Correct use of OpenStackCompareReleases to ensure that releases
between ocata and queens don't automatically enable fernet
token behaviour.

Change-Id: I6db8d006ceac7b61e69f547682c5a49d876cfec6
Closes-Bug: 1816807