rootwrap config files reference deleted quantum binaries

dhcp and l3 rootwrap filter files contain reference to the deleted
binary quantum-ns-metadata-proxy. This change removes these obsolete
filters.

Change-Id: Iad4772752d74a1c0535144b5faf9a1f8ae89f6a3
Closes-Bug: #1391256
Remove openvswitch core plugin entry point

The openvswitch core plugin has been removed but not its associated
"neutron.core_plugins" entry point. This change removes it from
setup.cfg.

Change-Id: I79f7c334cdeb0f4d0d68743734f69c0ec8523467
Related-Bug: #1323729
Closes-Bug: #1391326
Merge "rootwrap config files reference deleted quantum binaries"
Merge "Remove openvswitch core plugin entry point"