RHV : Snapshot merge fails with Permission Denied error.

Issue

• Snapshot merge fails for VM reporting Permission denied errors.

• vdsm.log

2017-10-24 14:30:58,833-0500 INFO  (jsonrpc/0) [jsonrpc.JsonRpcServer] RPC call VM.merge failed (error 52) in 1.46 seconds (__init__:539)
2017-10-24 14:30:58,944-0500 ERROR (jsonrpc/1) [virt.vm] (vmId='b2140d9c-11c5-4a83-8eea-03f2773d49f0') Live merge failed (job: a6a623bc-119f-427c-b3d9-d184ad8b1a07) (vm:4926)
Traceback (most recent call last):
  File "/usr/share/vdsm/virt/vm.py", line 4924, in merge 
    bandwidth, flags)
  File "/usr/lib/python2.7/site-packages/vdsm/virt/virdomain.py", line 69, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/libvirtconnection.py", line 123, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/utils.py", line 1006, in wrapper
    return func(inst, *args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 678, in blockCommit
    if ret == -1: raise libvirtError ('virDomainBlockCommit() failed', dom=self)
libvirtError: internal error: unable to execute QEMU command 'block-commit': Could not reopen file: Permission denied
2017-10-24 14:30:58,961-0500 INFO  (jsonrpc/1) [vdsm.api] FINISH merge return={'status': {'message': 'Merge failed', 'code': 52}} from=::ffff:192.168.56.242,34134, flow_id=f25d92dd-eaff-4550-9dc2-1efb34f93f3b (api:52)

• Engine.log

2017-10-09 17:53:39,702-05 INFO  [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (default task-90) [] EVENT_ID: USER_REMOVE_SNAPSHOT(342), Correlation ID: b8310565-0435-4db5-a8ed-8733aed637f8, Job ID: b5ee0ea1-8a63-478b-bb21-53179d1d449c, Call Stack: null, Custom Event ID: -1, Message: Snapshot 'Automatic Snapshot' deletion for VM 'dmscollectorgpvm01' was initiated by admin@internal.
2017-10-09 17:53:39,970-05 INFO  [org.ovirt.engine.core.bll.snapshots.RemoveSnapshotSingleDiskLiveCommand] (DefaultQuartzScheduler3) [b8310565-0435-4db5-a8ed-8733aed637f8] Executing Live Merge command step 'EXTEND'
2017-10-09 17:53:39,992-05 INFO  [org.ovirt.engine.core.bll.MergeExtendCommand] (pool-5-thread-3) [b8310565-0435-4db5-a8ed-8733aed637f8] Running command: MergeExtendCommand internal: true. Entities affected :  ID: e31e53e2-14e4-46a2-abee-a88689cefd3c Type: Storage
2017-10-09 17:53:39,992-05 INFO  [org.ovirt.engine.core.bll.MergeExtendCommand] (pool-5-thread-3) [b8310565-0435-4db5-a8ed-8733aed637f8] Base and top image sizes are the same; no extension required
2017-10-09 17:53:39,992-05 INFO  [org.ovirt.engine.core.bll.snapshots.RemoveSnapshotSingleDiskLiveCommand] (DefaultQuartzScheduler3) [b8310565-0435-4db5-a8ed-8733aed637f8] Executing Live Merge command step 'EXTEND'
2017-10-09 17:53:42,079-05 INFO  [org.ovirt.engine.core.bll.snapshots.RemoveSnapshotSingleDiskLiveCommand] (DefaultQuartzScheduler8) [b8310565-0435-4db5-a8ed-8733aed637f8] Executing Live Merge command step 'MERGE'
2017-10-09 17:53:42,120-05 INFO  [org.ovirt.engine.core.bll.MergeCommand] (pool-5-thread-4) [b8310565-0435-4db5-a8ed-8733aed637f8] Running command: MergeCommand internal: true. Entities affected :  ID: e31e53e2-14e4-46a2-abee-a88689cefd3c Type: Storage
2017-10-09 17:53:42,121-05 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.MergeVDSCommand] (pool-5-thread-4) [b8310565-0435-4db5-a8ed-8733aed637f8] START, MergeVDSCommand(HostName = redhat-hypervisor-host1, MergeVDSCommandParameters:{runAsync='true', hostId='0da7752b-3fc9-481b-8265-3c910ef38073', vmId='b2140d9c-11c5-4a83-8eea-03f2773d49f0', storagePoolId='cc16da98-2316-4a57-8a23-ba7d433e05fe', storageDomainId='e31e53e2-14e4-46a2-abee-a88689cefd3c', imageGroupId='9969fd9b-9bad-4d03-8874-67551d40158a', imageId='3106fce8-c0e8-482a-a56c-540c2ec18839', baseImageId='c5cd9787-739c-4307-a5ce-01450ab20d08', topImageId='0d89ee92-55b7-4ec5-978c-8ed70434c38d', bandwidth='0'}), log id: 8fc1e2
2017-10-09 17:53:43,089-05 ERROR [org.ovirt.engine.core.vdsbroker.vdsbroker.MergeVDSCommand] (pool-5-thread-4) [b8310565-0435-4db5-a8ed-8733aed637f8] Failed in 'MergeVDS' method
2017-10-09 17:53:43,094-05 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (pool-5-thread-4) [b8310565-0435-4db5-a8ed-8733aed637f8] EVENT_ID: VDS_BROKER_COMMAND_FAILURE(10,802), Correlation ID: null, Call Stack: null, Custom Event ID: -1, Message: VDSM redhat-hypervisor-host1 command MergeVDS failed: Merge failed