CephFS driver fails to delete non-existent shares

[Goutham Pacha Ravi]

Description
===========

If a share fails to be created on a cephfs backend; but the record exists in manila, the next course of action would be to delete the share. However, the share deletion fails because the driver doesn't ignore non-existent shares as expected. This sets the share's status to "error_deleting". Getting out of this state will need administrator intervention; and even administrators cannot use a regular "reset-state and delete" approach; they'd need to use "--force" to cleanup the share.

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

A chronological list of steps which will help reproduce the issue you hit:
* Created a share that failed some backend check and caused the share to be set to "error"
* Tried to delete the failed share

- A list of manila/openstack client commands (with correct argument value)
$ openstack share network create --name share-net --description "Manila test network" --neutron-net-id ${NETWORKID} --neutron-subnet-id ${SUBNETID}
$ openstack share create NFS 1 \
    --name share-test-1 \
    --description "Share test" \
    --share-network share-net \
    --share-type default

$ openstack share list
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+
| ID | Name | Size | Share Proto | Status | Is Public | Share Type Name | Host | Availability Zone |
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+
| 61ebff81-5c48-43a5-a104-9438239a7e18 | share-test-1 | 1 | NFS | error | False | default | | nova |
| 6fde80a0-fa9f-46e2-8e74-d2219b20c654 | share-test-2 | 1 | NFS | available | False | default | | nova |
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+

$ openstack share set --status error share-test-1
$ openstack share delete share-test-1

$ openstack share list
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+
| ID | Name | Size | Share Proto | Status | Is Public | Share Type Name | Host | Availability Zone |
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+
| 61ebff81-5c48-43a5-a104-9438239a7e18 | share-test-1 | 1 | NFS | error_deleting | False | default | | nova |
| 6fde80a0-fa9f-46e2-8e74-d2219b20c654 | share-test-2 | 1 | NFS | available | False | default | | nova |
+--------------------------------------+--------------+------+-------------+----------------+-----------+-----------------+------+-------------------+

Expected result
===============
Share that failed to create gets deleted.

Actual result
=============
Share goes to "error_deleting" with this error in the manila share log: https://paste.opendev.org/show/b4rKQRM8AniBg3td3Efg/

(Share creation error: https://paste.opendev.org/show/bbTHRpy46ZGKHtYU5mjr/)

Environment
===========
1. OpenStack Wallaby
2. CephFS via NFS

[Vida Haririan (vhariria)]

Triage notes: the workaround needs an admin to use force delete, which is, undesirable in cases where the ceph share never existed - for example, when the share got scheduled to ceph, but failed.

See additional triage information at https://meetings.opendev.org/meetings/manila/2024/manila.2024-05-16-15.01.log.html