platform_backup partition should be validated before upgrading

[Frank Miller]

Brief Description
-----------------
To handle cases where a controller disk does not have the proper partition for platform_backup, the upgrade code should detect this and not allow the upgrade to continue.

Severity
--------
Major

Steps to Reproduce
------------------
Start with an AIO-SX system where the root disk does not have a platform_backup partition or the partition is not configured properly (not large enough or wrong type, ie not ext4). Perform a software uprgade.

Expected Behavior
------------------
Upgrade code should detect the faulty partition and not allow user to proceed.

Actual Behavior
----------------
Upgrade proceeds but the install then detects the bad partition and wipes the data and recreates the partition with the right size and type. The issue here is the upgrade will then fail as the data cannot be migrated from the N release to the N+1 release since the partition data was wiped.

Reproducibility
---------------
Seen once. Only seen on a system with an incorrect partition for platform_backup.

System Configuration
--------------------
AIO-SX

Branch/Pull Time/Commit
-----------------------
stx4.0 load

Last Pass
---------
n/a

Timestamp/Logs
--------------
n/a

Test Activity
-------------
testing

Workaround
----------
none

[Frank Miller (sensfan22)]

Marking as stx.5.0 gating - this would be a good item to check for upgrades.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: r/stx.4.0
Review: https://review.opendev.org/742565

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/742569

[OpenStack Infra (hudson-openstack)]

Change abandoned by David Sullivan (<email address hidden>) on branch: r/stx.4.0
Review: https://review.opendev.org/742565
Reason: Use review in master. I'll create a new review to cherry-pick to stx4

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/742569
Committed: https://git.openstack.org/cgit/starlingx/config/commit/?id=e33a8035742e61d81c6e41c0540852d9b71f3319
Submitter: Zuul
Branch: master

commit e33a8035742e61d81c6e41c0540852d9b71f3319
Author: David Sullivan <email address hidden>
Date: Wed Jul 22 20:26:23 2020 -0400

    Verify platform-backup partition before SX upgrade

    There are scenarios were the backup partition could be incorrectly
    formatted. This can result in the partition being wiped during an
    upgrade. As part of the upgrade health check we'll verify all the
    parameters of the backup partition.

    Change-Id: I28d8a39c2edfb34a7298dc30aaba5a6bdf7b0382
    Signed-off-by: David Sullivan <email address hidden>
    Closes-Bug: 1888424