Description of problem:
When creating a snapshot with memory there are two additional disks created, memory disk and a metadata disk. If we fail after their creation is completed they will be removed from the engine but remain on the storage

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


How reproducible:
100%

Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:
There is an attempt to remove them but it fails because the task creating the volume is already cleared and the revert attempt fails:

2018-04-18 14:19:27,960+03 INFO  [org.ovirt.engine.core.bll.CommandMultiAsyncTasks] (org.ovirt.thread.pool-6-thread-43) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] CommandMultiAsyncTasks::attachTask: Attaching task '799342fa-8776-4545-bf41-f26f48470f12' to command '0faf9de2-f09f-4346-8cc5-f0dd9fc70822'.
2018-04-18 14:19:27,994+03 INFO  [org.ovirt.engine.core.bll.tasks.AsyncTaskManager] (org.ovirt.thread.pool-6-thread-43) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] Adding task '799342fa-8776-4545-bf41-f26f48470f12' (Parent Command 'AddImageFromScratch', Parameters Type 'org.ovirt.engine.core.common.asynctasks.AsyncTaskParameters'), polling hasn't started yet..
2018-04-18 14:19:28,034+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (org.ovirt.thread.pool-6-thread-43) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] BaseAsyncTask::startPollingTask: Starting to poll task '799342fa-8776-4545-bf41-f26f48470f12'.
2018-04-18 14:19:31,269+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (DefaultQuartzScheduler6) [2d41f2e9] SPMAsyncTask::PollTask: Polling task '799342fa-8776-4545-bf41-f26f48470f12' (Parent Command 'AddImageFromScratch', Parameters Type 'org.ovirt.engine.core.common.asynctasks.AsyncTaskParameters') returned status 'running'.
2018-04-18 14:19:41,333+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (DefaultQuartzScheduler7) [3512f268] SPMAsyncTask::PollTask: Polling task '799342fa-8776-4545-bf41-f26f48470f12' (Parent Command 'AddImageFromScratch', Parameters Type 'org.ovirt.engine.core.common.asynctasks.AsyncTaskParameters') returned status 'finished', result 'success'.
2018-04-18 14:19:41,342+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (DefaultQuartzScheduler7) [3512f268] BaseAsyncTask::onTaskEndSuccess: Task '799342fa-8776-4545-bf41-f26f48470f12' (Parent Command 'AddImageFromScratch', Parameters Type 'org.ovirt.engine.core.common.asynctasks.AsyncTaskParameters') ended successfully.
2018-04-18 14:19:41,352+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (org.ovirt.thread.pool-6-thread-47) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] SPMAsyncTask::ClearAsyncTask: Attempting to clear task '799342fa-8776-4545-bf41-f26f48470f12'
2018-04-18 14:19:41,355+03 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.SPMClearTaskVDSCommand] (org.ovirt.thread.pool-6-thread-47) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] START, SPMClearTaskVDSCommand( SPMTaskGuidBaseVDSCommandParameters:{runAsync='true', storagePoolId='5ad33afd-009f-0144-0197-0000000001de', ignoreFailoverLimit='false', taskId='799342fa-8776-4545-bf41-f26f48470f12'}), log id: 66513807
2018-04-18 14:19:41,356+03 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.HSMClearTaskVDSCommand] (org.ovirt.thread.pool-6-thread-47) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] START, HSMClearTaskVDSCommand(HostName = host, HSMTaskGuidBaseVDSCommandParameters:{runAsync='true', hostId='8c3b55e1-c296-4546-aee6-5b78ab37faf4', taskId='799342fa-8776-4545-bf41-f26f48470f12'}), log id: 46e22134
2018-04-18 14:19:41,456+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (org.ovirt.thread.pool-6-thread-47) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] BaseAsyncTask::removeTaskFromDB: Removed task '799342fa-8776-4545-bf41-f26f48470f12' from DataBase
2018-04-18 14:21:38,608+03 WARN  [org.ovirt.engine.core.bll.tasks.AsyncTaskManager] (DefaultQuartzScheduler2) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] Polling tasks. Task ID '799342fa-8776-4545-bf41-f26f48470f12' doesn't exist in the manager -> assuming 'finished'.
2018-04-18 14:21:38,613+03 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.SPMRevertTaskVDSCommand] (DefaultQuartzScheduler2) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] START, SPMRevertTaskVDSCommand( SPMTaskGuidBaseVDSCommandParameters:{runAsync='true', storagePoolId='5ad33afd-009f-0144-0197-0000000001de', ignoreFailoverLimit='false', taskId='799342fa-8776-4545-bf41-f26f48470f12'}), log id: 12c42fb7
2018-04-18 14:21:38,641+03 ERROR [org.ovirt.engine.core.vdsbroker.vdsbroker.HSMRevertTaskVDSCommand] (DefaultQuartzScheduler2) [257ecc4d-c7e0-4529-9a1d-e321dcdc16e0] Trying to revert unknown task '799342fa-8776-4545-bf41-f26f48470f12'


In Vdsm:
2018-04-18 14:19:28,195+0300 INFO  (jsonrpc/5) [vdsm.api] START createVolume(sdUUID=u'edc4aa26-e4f4-41d5-b325-6ec6fd7da9bb', spUUID=u'5ad33afd-009f-0144-0197-0000000001de', imgUUID=u'4863bfdb-dce5-4fbf-bc09-fad1aee22eaf', size=u'10240', volFormat=5, preallocate=1, diskType=2, volUUID=u'e5cbf97e-f7f1-4bd6-a90d-adc0165e201d', desc=u'{"DiskAlias":"snapshot_metadata","DiskDescription":""}', srcImgUUID=u'00000000-0000-0000-0000-000000000000', srcVolUUID=u'00000000-0000-0000-0000-000000000000', initialSize=None) from=::ffff:10.35.206.92,56174, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=6e4b2753-e341-4327-be49-228e1a6a6683 (api:47)
2018-04-18 14:19:28,496+0300 INFO  (tasks/4) [storage.Volume] Changing volume u'/rhev/data-center/mnt/10.35.0.233:_root_storage__domains_sd5/edc4aa26-e4f4-41d5-b325-6ec6fd7da9bb/images/b83c1346-22a8-47ec-833d-6031603e8b99/d750c1a9-7be3-4b67-aada-f3bd93c74282' permission to 0660 (fileVolume:478)
2018-04-18 14:19:28,523+0300 INFO  (jsonrpc/5) [vdsm.api] FINISH createVolume return=None from=::ffff:10.35.206.92,56174, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=6e4b2753-e341-4327-be49-228e1a6a6683 (api:53)
2018-04-18 14:19:28,727+0300 INFO  (tasks/1) [storage.Volume] Creating volume 97e38253-dc90-4a35-b8ef-df96d25627f2 (volume:1192)
2018-04-18 14:19:29,005+0300 INFO  (periodic/3) [vdsm.api] START getVolumeSize(sdUUID=u'edc4aa26-e4f4-41d5-b325-6ec6fd7da9bb', spUUID=u'5ad33afd-009f-0144-0197-0000000001de', imgUUID=u'b83c1346-22a8-47ec-833d-6031603e8b99', volUUID=u'67bffbc4-48bd-4797-9a09-a40c7ca72f56', options=None) from=internal, task_id=4c1637aa-def9-426d-bf0e-cfc7e0b9e1d9 (api:47)
2018-04-18 14:19:29,007+0300 INFO  (periodic/3) [vdsm.api] FINISH getVolumeSize return={'truesize': '0', 'apparentsize': '1073741824'} from=internal, task_id=4c1637aa-def9-426d-bf0e-cfc7e0b9e1d9 (api:53)
2018-04-18 14:19:29,151+0300 INFO  (jsonrpc/5) [jsonrpc.JsonRpcServer] RPC call Volume.create succeeded in 0.96 seconds (__init__:311)
2018-04-18 14:19:29,151+0300 INFO  (tasks/6) [storage.ThreadPool.WorkerThread] START task 6e4b2753-e341-4327-be49-228e1a6a6683 (cmd=<bound method Task.commit of <vdsm.storage.task.Task instance at 0x7fecec04a5f0>>, args=None) (threadPool:208)

------------- Revert attempt --------------------------
2018-04-18 14:21:38,625+0300 INFO  (jsonrpc/7) [vdsm.api] START revertTask(taskID=u'799342fa-8776-4545-bf41-f26f48470f12', spUUID=None, options=Non
e) from=::ffff:10.35.206.92,56874, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=190fd7fd-fbe2-44cf-90c6-d0fa53a4a112 (api:47)
2018-04-18 14:21:38,625+0300 INFO  (jsonrpc/7) [vdsm.api] FINISH revertTask error=Task id unknown: (u'799342fa-8776-4545-bf41-f26f48470f12',) from=
::ffff:10.35.206.92,56874, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=190fd7fd-fbe2-44cf-90c6-d0fa53a4a112 (api:51)
2018-04-18 14:21:38,625+0300 ERROR (jsonrpc/7) [storage.TaskManager.Task] (Task='190fd7fd-fbe2-44cf-90c6-d0fa53a4a112') Unexpected error (task:875)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/storage/task.py", line 882, in _run
    return fn(*args, **kargs)
  File "<string>", line 2, in revertTask
  File "/usr/lib/python2.7/site-packages/vdsm/common/api.py", line 49, in method
    ret = func(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/hsm.py", line 2288, in revertTask
    return self.taskMng.revertTask(taskID=taskID)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/taskManager.py", line 165, in revertTask
    t = self.__getTask(taskID)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/taskManager.py", line 85, in __getTask
    raise se.UnknownTask(taskID)
UnknownTask: Task id unknown: (u'799342fa-8776-4545-bf41-f26f48470f12',)
2018-04-18 14:21:38,625+0300 INFO  (jsonrpc/7) [storage.TaskManager.Task] (Task='190fd7fd-fbe2-44cf-90c6-d0fa53a4a112') aborting: Task is aborted: 
u"Task id unknown: (u'799342fa-8776-4545-bf41-f26f48470f12',)" - code 100 (task:1181)
2018-04-18 14:21:38,625+0300 ERROR (jsonrpc/7) [storage.Dispatcher] FINISH revertTask error=Task id unknown: (u'799342fa-8776-4545-bf41-f26f48470f1
2',) (dispatcher:82)
2018-04-18 14:21:38,625+0300 INFO  (jsonrpc/7) [jsonrpc.JsonRpcServer] RPC call Task.revert failed (error 401) in 0.00 seconds (__init__:311)
2018-04-18 14:21:38,789+0300 INFO  (jsonrpc/3) [vdsm.api] START revertTask(taskID=u'6e4b2753-e341-4327-be49-228e1a6a6683', spUUID=None, options=Non
e) from=::ffff:10.35.206.92,56874, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=989bb575-c599-4ef9-b23f-f14cb17cee99 (api:47)
2018-04-18 14:21:38,789+0300 INFO  (jsonrpc/3) [vdsm.api] FINISH revertTask error=Task id unknown: (u'6e4b2753-e341-4327-be49-228e1a6a6683',) from=::ffff:10.35.206.92,56874, flow_id=257ecc4d-c7e0-4529-9a1d-e321dcdc16e0, task_id=989bb575-c599-4ef9-b23f-f14cb17cee99 (api:51)