OSTF test for Glance failed because of bug in Ceph backend

Detailed bug description:
OSTF test "Launch instance, create snapshot, launch instance from snapshot" failed at the step 3. Make snapshot of the created instance.

Steps to reproduce:
1. Install MOS 8.0 with standalone-ceph plugin
https://github.com/dmdmitriev/fuel-plugin-standalone-ceph
2. Deploy environment with 3 controllers, 3 Ceph controllers (plugin), 3 Ceph storage, Mongo for Ceilometer, compute.
3. Run OSTF.

Expected results:
Successfull finish of OSTF testing.

Actual result:
OSTF run failed.

Description of the environment:
- Network model: Neutron with tunneling segmentation

Additional information:
After OSTF test fails, there is a VM snapshot, that left in Glance:
# glance image-list
+--------------------------------------+-------------------------------+
| ID | Name |
+--------------------------------------+-------------------------------+
| c9396969-c3df-40e9-8f2c-948d6de486de | ost1_test-snapshot-1961534293 |
| cb94978e-8946-4fa2-8737-ff6bf75410e9 | TestVM |
+--------------------------------------+-------------------------------+

# glance -d image-show ost1_test-snapshot-1961534293
Request returned failure status 404.
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/glanceclient/shell.py", line 688, in main
    args.func(client, args)
  File "/usr/lib/python2.7/dist-packages/glanceclient/v2/shell.py", line 193, in do_image_show
    image = gc.images.get(args.id)
  File "/usr/lib/python2.7/dist-packages/glanceclient/v2/images.py", line 181, in get
    resp, body = self.http_client.get(url)
  File "/usr/lib/python2.7/dist-packages/keystoneclient/adapter.py", line 170, in get
    return self.request(url, 'GET', **kwargs)
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/http.py", line 333, in request
    return self._handle_response(resp)
  File "/usr/lib/python2.7/dist-packages/glanceclient/common/http.py", line 89, in _handle_response
    raise exc.from_response(resp, resp.content)
HTTPNotFound: 404 Not Found: No image found with ID ost1_test-snapshot-1961534293 (HTTP 404)
404 Not Found: No image found with ID ost1_test-snapshot-1961534293 (HTTP 404)

# glance -d image-delete ost1_test-snapshot-1961534293
Request returned failure status 404.
No image with an ID of 'ost1_test-snapshot-1961534293' exists.

But I can check image's details in Horizon:
Image Details: ost1_test-snapshot-1961534293
Image Overview
Information

Name ost1_test-snapshot-1961534293
ID c9396969-c3df-40e9-8f2c-948d6de486de
Owner 6abccf8c0b2f45a29eb754c9b7f6b30f
Status Active
Public No
Protected No
Checksum 6b7a6d92ad4f87d2882654008079286a
Created July 21, 2016, 9:42 a.m.
Updated July 21, 2016, 9:44 a.m.

Specs
Size 39.2 MB
Container Format BARE
Disk Format RAW
Min RAM 64MB

Custom Properties
base_image_ref cb94978e-8946-4fa2-8737-ff6bf75410e9
image_location snapshot
image_state available
image_type snapshot
instance_uuid 79cce771-23c7-45d9-ad0f-9845f82c8359
owner_id 6abccf8c0b2f45a29eb754c9b7f6b30f
user_id 881bbbf93d3d4b0bbf92708e60b15458

If I check Ceph for that snapshot directly, I can see this:
# rbd -p images list
4284f796-3eef-4ccb-9c4f-77053ff3f438
5180c7f4-bb79-4f6f-ae1d-9e4499d5c26d
64e036e8-b314-4484-8f31-bd3601035dc9
c9396969-c3df-40e9-8f2c-948d6de486de
cb94978e-8946-4fa2-8737-ff6bf75410e9
# rbd snap ls -p images c9396969-c3df-40e9-8f2c-948d6de486de
SNAPID NAME SIZE
    16 snap 40162 kB
# rbd children images/c9396969-c3df-40e9-8f2c-948d6de486de@snap
compute/de6027ce-1d48-4706-9bad-4da8c228a876_disk

There is no VMs, running at this moment, so I don't know why there is a compute/..._disk still in Ceph.

If I'll try to do everything manually (run a VM from image, make a snapshot from VM, run another Vm from snapshot, check that second VM works well, delete second VM, delete snapshot), there is no errors at all.