Old leader added to the gcom list causes attempted restart after cold boot

[David Ames]

The config changed function tries to speed up cluster formation by adding the leader ip as seen in leader-settings.

In the case of a cold boot, the leader has almost certainly changed. This can lead to a non-leader node adding itself to the list. The consequence of which is the mysqld.cnf file changes and the charm mistakenly attempts to restart mysql rather than recognizing it is down.

This impedes the cold start bootstrap process.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/674059

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/674059
Committed: https://git.openstack.org/cgit/openstack/charm-percona-cluster/commit/?id=475b889020271dd09003fafc5459d1a2617ce0a5
Submitter: Zuul
Branch: master

commit 475b889020271dd09003fafc5459d1a2617ce0a5
Author: David Ames <email address hidden>
Date: Thu Aug 1 07:55:06 2019 -0700

    Do not add former leader to hosts

    After a cold boot, the leader has likely changed. Do not add this node
    as a former leader to the hosts list. This may cause changes to
    mysqld.cnf and an unwanted attempted restart of mysql.

    Change-Id: I5fc4b7822a4550e53e97655771938a903f92fcb1
    Close-Bug: #1838648