allow scheduling to disabled manila-share host

[kiran pawar]

Problem
=======
When deploying to a dedicated host with scheduler-hints a cloud admin wants to be able to do this even if the service is disabled. The reason for disablement may be:

1) Integration - the backend is being added newly. I want to schedule shares to test if everything is working before making it generally available.
2) maintenance - after a backend upgrade I want to confirm share creation is still working before making it generally available again

Having this would remove the need to do an extra re-start/deployment with a configuration change. Enabling the service can be done via API. We currently don't have a such a procedure, maintenances are done without disabling the backend.

Solution
========
A) If the scheduler gets a request containing scheduler hints it should consider all manila-share backends

 OR

B)[preferred] using scheduler hints the share gets scheduled directly without going to the scheduler

Consider remarks in https://etherpad.opendev.org/p/caracal-ptg-manila-operator-hour

[Vida Haririan (vhariria)]

See related comments in manila-dalmatian-m2-bugsquash ethercal https://ethercalc.net/o2qsmjpagsfb

[Vida Haririan (vhariria)]

See additional triage information at https://meetings.opendev.org/meetings/manila/2024/manila.2024-07-18-15.00.log.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/manila/+/925902

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/manila/+/925902
Committed: https://opendev.org/openstack/manila/commit/203a5e325f12d92bbf1edc21f606d4c391ef4268
Submitter: "Zuul (22348)"
Branch: master

commit 203a5e325f12d92bbf1edc21f606d4c391ef4268
Author: Kiran Pawar <email address hidden>
Date: Wed Aug 7 16:33:08 2024 +0000

    Allow scheduling to disabled manila-share host

    - Only allow to admin user and with 'only_host' scheduler hint

    In all other cases, scheduler will ignore disabled host. Please note,
    'disabled' host is up/running(i.e. listening on RPC calls), but
    disabled using share service set API.

    Closes-bug: #2072552
    Change-Id: Iaaa4e274d47cf2eaa0247234f268fdb5ff24461b