Unable to delete an invalid host from the simplex subcloud

[Junfeng Li]

Brief Description:
------------------

When a host is added by mistake to a simplex system, this invalid host can't be deleted from the command line.

Severity
--------
Minor: The user is not supposed to add a host to a simplex system. This fix is to allow delete it from CLI.

Steps to Reproduce
------------------
In a distributed cloud environment, add a simplex subcloud. After this subcloud is up and running, add another controller to it. As soon as this controller is powered up, the controller-0 host list will show the 2nd controller that is invalid. Cmd host-delete doesn't allow to delete the invalid host.

Expected Behavior
------------------
Allow deleting the invalid host

Actual Behavior
----------------
Deletion is not allowed

Reproducibility
---------------
100%

System Configuration
--------------------
Distributed cloud with one simplex subcloud

Branch/Pull Time/Commit
-----------------------
Unknown

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/config/+/845296

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/config/+/845303

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Junfeng Li <email address hidden>" on branch: master
Review: https://review.opendev.org/c/starlingx/config/+/845296
Reason: Wrong commit

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/config/+/845303
Committed: https://opendev.org/starlingx/config/commit/693a85bad13b353f2aee227b473e553db0cc6151
Submitter: "Zuul (22348)"
Branch: master

commit 693a85bad13b353f2aee227b473e553db0cc6151
Author: Junfeng Li <email address hidden>
Date: Thu Jun 9 18:22:00 2022 -0400

    Prevent a new host to be added to AIO-SX

    Details: 1. Added a condition check to prevent a host from being added to an AIO-SX.
             2. Updated host delete() to allow hosts to be deleted if it is not controller-0 in AIO-SX

    Closes-Bug: 1978134

    Test Plan:
    PASS: Unit test cases against non controller-0 AIO-SX host deletion
    PASS: Patched local simplex system and ran reproduced steps
    PASS: Migration from SX to DX

    Signed-off-by: Junfeng Li <email address hidden>

    Change-Id: I3510bc43f13869ec76673ec50a879b463ee760f4