upgrade_tasks fail to cleanup services

[Emilien Macchi]

UpgradeRemoveUnusedPackages parameter is supposed to enable some upgrade_tasks in charge of cleaning up the services after an upgrade (e.g. remove rpms), but some tasks don't work properly (ordering issue) and some of them work but aren't idempotent (fail if the upgrade run for a second time).

This bug is to track what is being done to address these problems.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/571229

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/571229
Committed: https://git.openstack.org/cgit/openstack/python-tripleoclient/commit/?id=328b0f53f1b828ca58fb6f7bf9b80149b3accfbf
Submitter: Zuul
Branch: master

commit 328b0f53f1b828ca58fb6f7bf9b80149b3accfbf
Author: Emilien Macchi <email address hidden>
Date: Wed May 30 08:26:03 2018 -0700

    Mark upgrade_cleanup option as experimental

    The feature doesn't work now, the upgrade_tasks that take care of the
    cleanup are being refactored by the Upgrade team. The current status of
    this feature is that the upgrade will fail in some of the tasks, and
    also the tasks aren't idempotent (for the ones which worked).

    Until we stabilize it, let's mark it as experimental.

    Related-Bug: #1774219
    Change-Id: I38c411cae75c419af18a654c741a014502ecd292