RHEV VM migration fails with libvirtError: Requested operation is not valid: domain has an active block job

Issue

• It is impossible to migrate a VM to a different hypervisor. The following error is seen in the engine.log:

Failed to migrate
Traceback (most recent call last):
  File "/usr/share/vdsm/vm.py", line 325, in run
    self._startUnderlyingMigration(startTime)
  File "/usr/share/vdsm/vm.py", line 408, in _startUnderlyingMigration
    None, maxBandwidth)
  File "/usr/share/vdsm/vm.py", line 867, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/vdsm/libvirtconnection.py", line 76, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 1178, in migrateToURI2
    if ret == -1: raise libvirtError ('virDomainMigrateToURI2() failed', dom=self)
libvirtError: Requested operation is not valid: domain has an active block job