'Enable the current instance\'s availability zone in the provided lb.
Returns True if the zone was enabled or False if no change was made.
lb: load balancer'

def _enable_availailability_zone(self, lb):

    instance = self._get_instance()
    if (instance.placement in lb.availability_zones):
        return False
    lb.enable_zones(zones=instance.placement)
    return (instance.placement in lb.availability_zones)
