Description of problem:
When two (or more) VMs have attached same ISO as CDROM and one of the VMs is shutting down, it logs an error in vdsm logs. The error is actually ignored and shutdown is successful, but it pollutes the log and requires more time for shutdown due to lvm command retries. We should have a way to detect that ISO is used by another VM and skip deactivation of the volume or at least ignore the error completely.


How reproducible:
always

Steps to Reproduce:
1. Start 2 VMs
2. Attach same ISO as CD to both VMs
3. Shut down one of the VMs

Actual results:
Error log in vdsm log

Expected results:
No error in the log

Additional info:
vdsm exception:

2020-08-17 09:35:26,099-0400 INFO  (libvirt/events) [vdsm.api] FINISH teardownImage error=Cannot deactivate Logical Volume: ('General Storage Exception: ("5 [] [\'  Logical volume aee38bf8-9f69-4a56-b30a-6e1cf6e1355f/51067df7-c19d-4d4f-945e-d26cc1e95db6 in use.\']\\naee38bf8-9f69-4a56-b30a-6e1cf6e1355f/[\'51067df7-c19d-4d4f-945e-d26cc1e95db6\']",)',) from=internal, task_id=840d7cfc-32bb-4f7f-b072-d25b396f3fcb (api:52)
2020-08-17 09:35:26,099-0400 ERROR (libvirt/events) [storage.TaskManager.Task] (Task='840d7cfc-32bb-4f7f-b072-d25b396f3fcb') Unexpected error (task:880)
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/vdsm/storage/lvm.py", line 1189, in _setLVAvailability
    changelv(vg, lvs, ("--available", available))
  File "/usr/lib/python3.6/site-packages/vdsm/storage/lvm.py", line 1184, in changelv
    raise se.StorageException("%d %s %s\n%s/%s" % (rc, out, err, vg, lvs))
vdsm.storage.exception.StorageException: General Storage Exception: ("5 [] ['  Logical volume aee38bf8-9f69-4a56-b30a-6e1cf6e1355f/51067df7-c19d-4d4f-945e-d26cc1e95db6 in use.']\naee38bf8-9f69-4a56-b30a-6e1cf6e1355f/['51067df7-c19d-4d4f-945e-d26cc1e95db6']",)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/vdsm/storage/task.py", line 887, in _run
    return fn(*args, **kargs)
  File "<decorator-gen-169>", line 2, in teardownImage
  File "/usr/lib/python3.6/site-packages/vdsm/common/api.py", line 50, in method
    ret = func(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/vdsm/storage/hsm.py", line 3295, in teardownImage
    dom.deactivateImage(imgUUID)
  File "/usr/lib/python3.6/site-packages/vdsm/storage/blockSD.py", line 1313, in deactivateImage
    lvm.deactivateLVs(self.sdUUID, volUUIDs)
  File "/usr/lib/python3.6/site-packages/vdsm/storage/lvm.py", line 1705, in deactivateLVs
    _setLVAvailability(vgName, toDeactivate, "n")
  File "/usr/lib/python3.6/site-packages/vdsm/storage/lvm.py", line 1194, in _setLVAvailability
    raise error(str(e))
vdsm.storage.exception.CannotDeactivateLogicalVolume: Cannot deactivate Logical Volume: ('General Storage Exception: ("5 [] [\'  Logical volume aee38bf8-9f69-4a56-b30a-6e1cf6e1355f/51067df7-c19d-4d4f-945e-d26cc1e95db6 in use.\']\\naee38bf8-9f69-4a56-b30a-6e1cf6e1355f/[\'51067df7-c19d-4d4f-945e-d26cc1e95db6\']",)',)