Add /lib/modules to neutron_openvswitch_agent
Add /lib/modules to neutron_openvswitch_agent

On many systems IPv6 related modules are not loaded by default.
Usually when one runs ip6tables-* commands required modules are
probed. In neutron_openvswitch_agent container /lib/modules
does not exist. The commands fail to process ip6 firewall
rules as consequence.

Change-Id: Ic4e72eb4f5304f013b7a09ddd31794cfafa67e0b
Closes-Bug: #1615715

dardelean/kolla-ansible,dardelean/kolla-ansible,dardelean/kolla-ansible