Description of problem:
When vm is running, deleting snapshot of it fails with 'Live merge failed' error on vdsm host.

2019-12-04 12:08:29,692+0000 ERROR (jsonrpc/0) [virt.vm] (vmId='ea2f390f-f7f2-463b-a511-3115b17205a9') Live merge failed (job: ef5af19e-195d-44d0-959a-84fa46bc5739) (vm:5583)
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/vdsm/virt/vm.py", line 5581, in merge
    bandwidth, flags)
  File "/usr/lib/python3.6/site-packages/vdsm/virt/virdomain.py", line 101, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/vdsm/common/libvirtconnection.py", line 131, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib/python3.6/site-packages/vdsm/common/function.py", line 94, in wrapper
    return func(inst, *args, **kwargs)
  File "/usr/lib64/python3.6/site-packages/libvirt.py", line 728, in blockCommit
    if ret == -1: raise libvirtError ('virDomainBlockCommit() failed', dom=self)
libvirt.libvirtError: internal error: qemu block name 'json:{"backing": {"driver": "qcow2", "file": {"driver": "host_device", "filename": "/rhev/data-center/mnt/blockSD/66c682f4-d084-4144-afdf-c15f25c6e3ce/images/5dd7d38b-4187-4635-93b6-c5577c761964/ca837c6a-0633-4276-bec0-a0dd0b67d971"}}, "driver": "qcow2", "file": {"driver": "host_device", "filename": "/rhev/data-center/mnt/blockSD/66c682f4-d084-4144-afdf-c15f25c6e3ce/images/5dd7d38b-4187-4635-93b6-c5577c761964/792e486b-1d16-4185-955c-a0d67cab4d4b"}}' doesn't match expected '/rhev/data-center/mnt/blockSD/66c682f4-d084-4144-afdf-c15f25c6e3ce/images/5dd7d38b-4187-4635-93b6-c5577c761964/792e486b-1d16-4185-955c-a0d67cab4d4b'


Engine error:
http://pastebin.test.redhat.com/819049

Version-Release number of selected component (if applicable):
rhv-release-4.4.0-4
vdsm-4.40.0-141.gitb9d2120.el8ev.x86_64
Engine rhel7, host rhel8

How reproducible:
100%

Steps to Reproduce:
1. Power on the vm, create snapsot of it, remove the snapshot


Actual results:
Removal of snapshot fails

Expected results:
Shouldnt fail

Additional info:
log collector files for engine + relevant host are attached in private message below.