Comment 2 for bug 1582598

Reviewed: https://review.openstack.org/317600
Committed: https://git.openstack.org/cgit/openstack/networking-bgpvpn/commit/?id=ccc13f755b66c32757a1505a073ab5316642d3b2
Submitter: Jenkins
Branch: master

commit ccc13f755b66c32757a1505a073ab5316642d3b2
Author: Thomas Morin <email address hidden>
Date: Tue May 17 17:45:35 2016 +0200

    bagpipe: really use the extension-specific cookie

    The code in OVSBridgeIntercept was not behaving
    as intended:
    - the extension cookie was not applied as expected, even
      for the ofctl-based OVSTunnelBridge (interference with
      class inheritance, because __getattr__ does not let us
      override methods existing in a parent class,
      __getattribute__ has to be used instead)
    - the extension cookie would never have been applied
      for the native.OVSTunnelBridge that does not use add_flow

    This changes corrects the code and adds a test case.

    We also now import the neutron constants from neutron-lib.

    Change-Id: I779d7a8bf7fc31d936d1e401e4726711c8404ed2
    Closes-Bug: 1582598