Description of problem:
RBD Retype if failing when running tempest.api.volume.admin.test_volume_retype.VolumeRetypeWithMigrationTest.test_volume_from_snapshot_retype_with_migration from [1].  This is a multi-backend deployment consisting of RBD, NFS, NETAPP, and ISCSI.  Any instance where the test attempts to retype the RBD volume to the other backend it will fail the testcase. Retyping from another backend to RBD does not show any issues.  Below results are from RBD to NFS.

(overcloud) [stack@undercloud-0 tempest_workspace]$ tempest run --serial --regex tempest.api.volume.admin.test_volume_retype
{0} tempest.api.volume.admin.test_volume_retype.VolumeRetypeWithMigrationTest.test_available_volume_retype_with_migration [27.072103s] ... ok
{0} tempest.api.volume.admin.test_volume_retype.VolumeRetypeWithMigrationTest.test_volume_from_snapshot_retype_with_migration [304.284310s] ... FAILED

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    b'Traceback (most recent call last):'
    b'  File "/usr/lib/python3.6/site-packages/tempest/api/volume/admin/test_volume_retype.py", line 142, in test_volume_from_snapshot_retype_with_migration'
    b'    src_vol = self._create_volume_from_snapshot()'
    b'  File "/usr/lib/python3.6/site-packages/tempest/api/volume/admin/test_volume_retype.py", line 67, in _create_volume_from_snapshot'
    b"    self.snapshots_client.wait_for_resource_deletion(snapshot['id'])"
    b'  File "/usr/lib/python3.6/site-packages/tempest/lib/common/rest_client.py", line 899, in wait_for_resource_deletion'
    b'    raise exceptions.TimeoutException(message)'
    b'tempest.lib.exceptions.TimeoutException: Request timed out'
    b'Details: (VolumeRetypeWithMigrationTest:test_volume_from_snapshot_retype_with_migration) Failed to delete volume-snapshot 81982518-e552-4f6e-a805-0647e9ea2cbf within the required time (300 s).'
    b''


Version-Release number of selected component (if applicable):
16.1

How reproducible:
100% reproducible

Steps to Reproduce:
1. Create a multi-backend deployment consisting of RBD backend and another backend
2. Execute tempest test tempest.api.volume.admin.test_volume_retype.VolumeRetypeWithMigrationTest.test_volume_from_snapshot_retype_with_migration
3.

Actual results:
Testcase times out when attempting to clean up snapshot

Expected results:
Test should successfully retype the volume created from the snapshot from RBD to destination backend


Additional info:

[1] https://github.com/openstack/tempest/blob/master/tempest/api/volume/admin/test_volume_retype.py#L141