Make it easier to use jumbo frames

[Adrien Cunin]

This is a wishlist bug.

It'd be nice to have os_neutron support https://docs.openstack.org/neutron/latest/admin/config-mtu.html (without having to use config overrides).

Can we imagine a way of using the `container_mtu` parameter to automatically configure Neutron according to this documentation page?

[Alexey 'Fenuks' Rusetsky (fenuks-uh)]

This can be done using config overrides in user_variable.yml, for example:

neutron_neutron_conf_overrides:
  DEFAULT:
    global_physnet_mtu: 9000
neutron_ml2_conf_ini_overrides:
  ml2:
    path_mtu: 1500

Since you need to set container_mtu in openstack-ansible manually, this looks like the best way to configure Neutron.