'Get the vmdk file name of the backing.
The vmdk file path of the backing returned is of the form:
"[datastore1] my_folder/my_vm.vmdk"
:param backing: Reference to the backing
:return: VMDK file path of the backing'

def get_vmdk_path(self, backing):

    disk_device = self._get_disk_device(backing)
    backing = disk_device.backing
    if (backing.__class__.__name__ != 'VirtualDiskFlatVer2BackingInfo'):
        msg = (_('Invalid    disk    backing:    %s.') % backing.__class__.__name__)
        LOG.error(msg)
        raise AssertionError(msg)
    return backing.fileName
