Proactive checks to be done before Juju Contrail Upgrade

Without these proactive steps juju upgrade may face issues.

Proactive checks to be done before Juju Contrail Upgrade.

On each juju node make sure there is enough disk space available.

Make sure all the docker containers are responding and are not in stuck state.

Make sure docker login is successful.

Make sure repo access is proper and verify container image download using docker pull command. 

Make sure all contrail units are in active state before starting upgrade. (contrail-status should be active in all juju units)

Take contrail backup in json format before we start the upgrade.