Comment 0 for bug 1929884

Brief Description
-----------------
When performing a software upgrade of an AIO-DX system, if the upgrade is aborted after both controllers have been upgraded, the documentation indicates that it should be possible to abort the upgrade and downgrade the controllers.

It turns out that there is a file permission issue blocking the host-downgrade command for controller-0

Note: this is a very low priority issue, an abort would normally never happen, and if it did it would normally occur much earlier in the procedure. Also, very few people are doing upgrades.

Severity
--------
Minor

Steps to Reproduce
------------------
Perform a platform upgrade of an AIO-DX system, up to the point where both controllers are unlocked.
Then do the following:
 - system upgrade-abort
 - (swact from controller-0 to controller-1 to make controller-1 active)
 - system host-lock controller-0
 - (wait for controller-0 to lock)
 - system host-downgrade controller-0

Expected Behavior
------------------
It should intitiate the downgrade

Actual Behavior
----------------
 system host-downgrade controller-0
[Errno 13] Permission denied: '/etc/platform/.upgrade_rollback'

Reproducibility
---------------
Reproducable

System Configuration
--------------------
AIO-DX (upgrading from custom r4 to custom r5)

Branch/Pull Time/Commit
-----------------------
Custom Load built May 25

Last Pass
---------
Unknown.

Timestamp/Logs
--------------
sysinv 2021-05-27 23:12:31.547 98746 ERROR wsme.api [-] Server-side error: "[Errno 13] Permission denied: '/etc/platform/.upgrade_rollback'". Detail:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/wsmeext/pecan.py", line 85, in callfunction
    result = f(self, *args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/sysinv/api/controllers/v1/host.py", line 2773, in downgrade
    open(tsc.UPGRADE_ROLLBACK_FLAG, "w").close()
IOError: [Errno 13] Permission denied: '/etc/platform/.upgrade_rollback'

Test Activity
-------------
Developer Testing

Workaround
----------
There is none.
A similar issue was encountered (and fixed) for another flag by this submission
https://review.opendev.org/c/starlingx/config/+/675673