Why live snapshot deletion (live merge) failed and cleanup thread is executed continuously in the vdsm side

Issue

• A live merge failed and the job is still showing in the RHV-M portal.
• A cleanup thread is executing continuously in the backend which does imageSyncVolumeChain and then tries to deactivate the leaf lv. However, it's failing with below error.

2017-10-12 14:56:55,007+0530 DEBUG (merge/c1ed19b5) [storage.Misc.excCmd] FAILED: <err> = '  Logical volume 8257cf14-d88d-4e4e-998c-9f8976dac2a2/ded1883f-94de-4510-8ddd-7ecc432e4009 in use.\n'; <rc> = 5 (commands:93)
2017-10-12 14:56:55,009+0530 ERROR (merge/c1ed19b5) [root] Unhandled exception (utils:374)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/utils.py", line 368, in wrapper
    return f(*a, **kw)
  File "/usr/share/vdsm/virt/vm.py", line 5287, in run
    self.teardown_top_volume()
  File "/usr/share/vdsm/virt/vm.py", line 5270, in teardown_top_volume
    self.job['topVolume'])
  File "/usr/share/vdsm/storage/blockSD.py", line 918, in teardownVolume
    lvm.deactivateLVs(self.sdUUID, [volUUID])
  File "/usr/share/vdsm/storage/lvm.py", line 1304, in deactivateLVs
    _setLVAvailability(vgName, toDeactivate, "n")
  File "/usr/share/vdsm/storage/lvm.py", line 843, in _setLVAvailability
    raise error(str(e))
CannotDeactivateLogicalVolume: Cannot deactivate Logical Volume: ('General Storage Exception: ("5 [] [\'  Logical volume 8257cf14-d88d-4e4e-998c-9f8976dac2a2/ded1883f-94de-4510-8ddd-7ecc432e4009 in use.\']\\n8257cf14-d88d-4e4e-998c-9f8976dac2a2/[u\'ded1883f-94de-4510-8ddd-7ecc432e4009\']",)',)
2017-10-12 14:56:55,028+0530 ERROR (merge/c1ed19b5) [root] Unhandled exception (utils:374)