Share group deletion fails due to already deleted share server

[Carlos Eduardo]

Description
===========
During the deletion of share network subnets, we are not checking for leftover share groups and preventing the deletion in case there are share groups in the subnet.

Steps to reproduce
==================

A chronological list of steps which will help reproduce the issue you hit:
* Create a share network
* Create a share group type and a share group in a DHSS True environment
* Create a share in the share group
* Delete the share
* Delete the share network subnet

Expected result
===============
Manila should prevent the deletion of the share network subnet, as there is a share group related to it.

Actual result
=============
Manila allows the deletion of the share network subnet, thus deleting the share server. When we request the deletion of the share group, it fails due to the share server not being known to Manila anymore.

Environment
===========
1. Devstack - Dummy Driver on DHSS=True (could happen with any DHSS=True backend)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/manila/+/872330

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/manila-tempest-plugin/+/875981
Committed: https://opendev.org/openstack/manila-tempest-plugin/commit/dab53f8e2b6d84114288ccf3c63751be8236cc57
Submitter: "Zuul (22348)"
Branch: master

commit dab53f8e2b6d84114288ccf3c63751be8236cc57
Author: silvacarloss <email address hidden>
Date: Wed Mar 1 16:28:05 2023 -0300

    Correct share group tests cleanup order

    Some share group tests were taking advantage of a bug in Manila.
    Share network subnets were being allowed to be deleted even when
    its share servers were tied to a share group. With that bug being
    fixed, we need to ensure that the share groups are deleted before
    the share network subnet alongside the share servers are.

    Related-Bug: #2004212
    Change-Id: I05607883c34bca586c795c7efab1df8d0edd6cff

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/manila/+/872330
Committed: https://opendev.org/openstack/manila/commit/2b52056721297b494a1d09b773b3d48666cc159f
Submitter: "Zuul (22348)"
Branch: master

commit 2b52056721297b494a1d09b773b3d48666cc159f
Author: silvacarloss <email address hidden>
Date: Tue Jan 31 13:22:08 2023 -0300

    Check share network for share groups before deletion

    Share network subnets were not checking for the existence of share
    groups while processing a delete request. Then, if a share network
    had a share server that was tied to a share group, it would end up
    deleting the share server, leaving the share group orphan. When we
    triggered the deletion of the share group, it would fail, as the
    share server was not known to Manila anymore.

    Fix that issue by adding an extra validation step during the share
    network subnet delete API.

    Closes-Bug: #2004212
    Depends-On: https://review.opendev.org/c/openstack/manila-tempest-plugin/+/875981
    Change-Id: I563bf925523fa44689c83f432ce5a460276afef7