Comment 4 for bug 1757044

Reviewed: https://review.openstack.org/568410
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=5e59cd2a5fcac205e3452efa20a1738c54834520
Submitter: Zuul
Branch: master

commit 5e59cd2a5fcac205e3452efa20a1738c54834520
Author: LIU Yulong <email address hidden>
Date: Mon May 14 14:16:26 2018 +0800

    Refactor for L3 router QoS extensions

    Move the l3 qos extensions to a separated folder,
    then we can move a following up router gateway IP
    QoS extension to it.

    And also extract some common code to a base class.

    Related-Bug: #1757044
    Change-Id: I63cc9506caa80f889ad817444281a0ac31bc9418