Fixing octavia-grenade job and disabling pylint warnings

grenade now updates from an ML2/OVN deployment. Octavia needs to source
the devstack/lib/octavia file from neutron, which provides the functions
that manage the octavia management interfaces.

The commit also removes false-positive pylint warnings, an issue was
reported to the pylint project:
https://github.com/PyCQA/pylint/issues/8497

Change-Id: Ie26a154c320d8527e54b871a3b99bbbc3c2ee811

devstack/upgrade/shutdown.sh

@@ -16,6 +16,8 @@ OCTAVIA_DEVSTACK_DIR=$(dirname $(dirname $0))
 source $OCTAVIA_DEVSTACK_DIR/settings
 source $OCTAVIA_DEVSTACK_DIR/plugin.sh
 
+source ${GITDIR[neutron]}/devstack/lib/octavia
+
 set -o xtrace
 
 octavia_stop

octavia/amphorae/backends/agent/api_server/plug.py

@@ -246,6 +246,8 @@ class Plug(object):
         try:
             with pyroute2.IPRoute() as ipr:
                 idx = ipr.link_lookup(address=mac)[0]
+                # Workaround for https://github.com/PyCQA/pylint/issues/8497
+                # pylint: disable=E1136, E1121
                 addr = ipr.get_links(idx)[0]
                 for attr in addr['attrs']:
                     if attr[0] == consts.IFLA_IFNAME:

octavia/amphorae/backends/utils/interface.py

@@ -181,6 +181,8 @@ class InterfaceController(object):
         with pyroute2.IPRoute() as ipr:
             idx = ipr.link_lookup(ifname=interface.name)[0]
 
+            # Workaround for https://github.com/PyCQA/pylint/issues/8497
+            # pylint: disable=E1136, E1121
             link = ipr.get_links(idx)[0]
             current_state = link.get(consts.STATE)
 
@@ -370,6 +372,8 @@ class InterfaceController(object):
         with pyroute2.IPRoute() as ipr:
             idx = ipr.link_lookup(ifname=interface.name)[0]
 
+            # Workaround for https://github.com/PyCQA/pylint/issues/8497
+            # pylint: disable=E1136, E1121
             link = ipr.get_links(idx)[0]
             current_state = link.get(consts.STATE)