'Migrate volume to another host using retype.
:param ctxt: context
:param volume: the volume object including the volume_type_id
:param new_type: the new volume type.
:param diff: difference between old and new volume types.
Unused in driver.
:param host: the host dict holding the relevant
target(destination) information
:returns: boolean -- True if retype succeeded, False if error'

def retype(self, ctxt, volume, new_type, diff, host):

    return self.common.retype(volume, new_type, host)
