ripngd: retrofit the 'redistribute' commands to the new northbound model

ripngd: retrofit the 'redistribute' commands to the new northbound model

Trivial conversion. As usual, combine multiple DEFUNs into a single
DEFPY for simplicity.

As a bonus of the northbound conversion, this commit fixes the
redistribution of certain protocols into ripngd. The 'redist_type'
array used by the "redistribute" commands was terribly outdated,
which was preventing the CLI to parse correctly certain protocols
like isis and babel.

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