[General] Remove l3_db.subscribe calls fron router plugins

[Sanket Sudake]

Removed from master:
https://github.com/openstack/neutron/blob/master/neutron/db/l3_db.py

Marked for removal in newton:
https://github.com/openstack/neutron/blob/stable/newton/neutron/db/l3_db.py#L1980

Removing l3_db.subscribe call should be safe enough. Change should work across releases from newton.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/505179

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sanket Sudake (<email address hidden>) on branch: master
Review: https://review.openstack.org/505179
Reason: Merging patch through existing review https://review.openstack.org/#/c/504923/3
Unable to merge current review due to circular dependency

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/504923
Committed: https://git.openstack.org/cgit/openstack/omni/commit/?id=38f171bdea86fcc9fce4065c04a8b997694bcdb7
Submitter: Jenkins
Branch: master

commit 38f171bdea86fcc9fce4065c04a8b997694bcdb7
Author: Sanket <email address hidden>
Date: Mon Sep 18 17:23:39 2017 +0530

    Unit tests fixes in nova and neutron

    Patch 1:
    [General] Removed unused parameters from InstanceInfo

    Many of unused parameters were removed from nova.virt.hardware.InstanceInfo in Pike.
    Same was notified to OOT(Out of tree) drivers.

    References:
    [1] https://review.openstack.org/#/c/471146/6/nova/virt/hardware.py
    [2] http://lists.openstack.org/pipermail/openstack-dev/2017-June/117962.html

    Closes-Bug: #1717907

    Patch 2:
    [General] Remove l3_db.subscribe calls from router plugins

    l3_db.subscribe has been deprecated from newton. Removing it
    was recently disabled from pike release.

    Refer bug description for more details.
    Closes-Bug: #1718180

    Change-Id: Ied1868736c4edb9da839d6d4b49aa1d98cbef251