firewall driver is an abstract class not using abstractmethod

[Isaku Yamahata]

FirewallDrifver uses @abstractmethod decorator, but it doesn't set its metaclass to ABCMeta.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/21495

[Cedric Brandily (cbrandily)]

That's the opposite: FirewallDriver is an abstract class using the pattern:

 def method(...):
    raise NotImplementedError

instead of:

 @abstractmethod
 def method(...):
   pass

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/239403

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/239403
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=e9ee5bd308bedd09eed1bf436852ec9898395ffc
Submitter: Jenkins
Branch: master

commit e9ee5bd308bedd09eed1bf436852ec9898395ffc
Author: Dariusz Smigiel (dasm) <email address hidden>
Date: Mon Oct 26 12:12:38 2015 +0100

    Add abstractmethod to FirewallDriver abstract class

    FirewallDriver is abstract base class but do not have abstractmethods.
    Updated methods to correspond with use-case of class.

    Closes-bug: #1119119
    Change-Id: I4b27b27d66c0b89cd9b65541cc1703103a2b00d2