'Make an existing migration record count for resource tracking.
If a migration record was created already before the request made
it to this compute host, only set up the migration so it\'s included in
resource tracking. This should be done while the
COMPUTE_RESOURCES_SEMAPHORE is held.'

def _claim_existing_migration(self, migration, nodename):

    migration.dest_compute = self.host
    migration.dest_node = nodename
    migration.dest_host = self.driver.get_host_ip_addr()
    migration.status = 'pre-migrating'
    migration.save()
