We were silently relying on some ofp actions to be decoded by the
default decoder which would yield decent string values.
In order to be more safe and robust, add an explicit decoder for all
missing actions.
This patch also reworks the learn action decoding to make it more
explicit and verify all the fields specified in the learn action are
actually valid fields.
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
