If roles are not settled (voters is not an odd number), leaving the
cluster might break things. Waiting for roles to settle before leaving,
and afterwards on the leader.
Pass force=1 when deleting cluster member.
Cluster removal happens when a juju unit is departing.
Change-Id: Ic9a7273be36a6cbb117b74bcfd94cef116a3b603
abf7310786