Changing flavor details results as admin results in flavor "Not Available" for non-admin users

[Rene Soto]

Detailed bug description:
In MOS 9.1 environment, I was able to reproduce the exact issue outlined in https://bugs.launchpad.net/horizon/+bug/1441523
where instance flavor is no longer available for a non-admin user after it is modified.

Steps to reproduce:
1. Install/use and all-in-one w/ demo project
2. As admin, create a flavor and assign to the demo project
3. Log out as admin and log in as demo (must not have admin privs)
4. As demo, launch an instance on this flavor in the demo project
5. Log out as demo and log in as admin
6. As admin, change the amount of RAM for the flavor
7. Log out as admin, log in as demo
8. Check the instances page and size should show "Not available" and there should be an error in the upper right saying "Error: Unable to retrieve instance size information."

Expected results:
Since modifying a flavor essentially "deletes" the original and creates a new one, we have to ensure that the non-admin user still has access to the original flavor after it is modified by an admin.

Actual result:
An error doesn't pop up in Horizon (as it occurs in the aforementioned Horizon bug), but the instance size still shows as "Not Available" for a non-admin user.

Reproducibility:
100%
Workaround:
Resize instance with available flavor

Impact:
Customer also mentioned that the instance hangs when it's in this state, but I haven't been able to reproduce that part just yet.

Description of the environment:
- Operation system: Ubuntu 14.04
- Versions of components: Mirantis OpenStack 9.1
- Reference architecture: N/A
- Network model: N/A
- Related projects installed: N/A
Additional information: N/A

[Rene Soto (rsoto)]

It may also be worth mentioning that this is not only observed in Horizon. Here, we can also see "Flavor not found" in the nova show output in the CLI:

root@node-1:~# nova show 0dbba63c-b12a-44de-a409-5b02e7688aa3
+--------------------------------------+----------------------------------------------------------+
| Property | Value |
+--------------------------------------+----------------------------------------------------------+
{truncated}
| description | testInstance |
| flavor | Flavor not found (27278f90-0afc-4fc9-a4b2-138a2b5802a9) |
| hostId | ba6d7e70d29b1d9c27087b96784e6a2912da7d086a2149ce50db1d37 |
| id | 0dbba63c-b12a-44de-a409-5b02e7688aa3 |
| image | TestVM (2d93532f-6285-44ce-b5d1-ee8dab748023) |
{truncated}
+--------------------------------------+----------------------------------------------------------+

[Roman Podoliaka (rpodolyaka)]

This is a known issue / existing behavior of Nova. In order to change it we'd need to propose a spec upstream.

>>> Impact: Customer also mentioned that the instance hangs when it's in this state, but I haven't been able to reproduce that part just yet.

Yeah, I don't think that's true: the only problem is that regular users are not allowed to read soft-deleted entries.

You can either resize the instances with deleted flavors or just forbid deletion of flavors in policy.json as a workaround for now.

As MOS (as it is) is in maintenance state now, I do not think we should do anything in downstream.