lxd/device/nic/routed: Ensure IP neighbour proxy entries are removed on stop
lxd/device/nic/routed: Ensure IP neighbour proxy entries are removed on stop

In cases of failed start, liblxc does not (currently) clean up IP neighbour entries added, so do this in LXD too.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

lxc/lxd,hallyn/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,stgraber/lxd,atxwebs/lxd,hallyn/lxd,stgraber/lxd