mysql-router upgrade reliability

Current upgrade plan for myql-router:

Upgrade plan for 'keystone-mysql-router' to 'victoria'
    Refresh 'keystone-mysql-router' to the latest revision of '8.0/stable'
    Wait for up to 300s for app 'keystone-mysql-router' to reach the idle state

The case is the charm failed during the refresh to 8.0/stable, and the package still the old version on the unit due to some environment issue.

In this case

COU wouldn't check the package version on the unit
If user re run COU, COU will consider it's finished because the channel is already the target version.
Also the configuration source is the still the old one, need to verify why COU doesn't include source configuration change step. $ juju config keystone-mysql-router source

Suggest solution:

Add package version check and the possible operation to fix it.

canonical / charmed-openstack-upgrader

mysql-router upgrade reliability #595