ripd: retrofit the 'network' command to the new northbound model

ripd: retrofit the 'network' command to the new northbound model

The frr-ripd YANG module models the ripd "network" command using two
separate leaf-lists for simplicity: one leaf-list for interfaces and
another leaf-list for actual networks. In the 'cli_show' callbacks,
display the "network" command for entries of both leaf-lists.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>