lib, zebra: add AFI parameter to the ZEBRA_REDISTRIBUTE_DEFAULT_* messages

lib, zebra: add AFI parameter to the ZEBRA_REDISTRIBUTE_DEFAULT_* messages

Some daemons like ospfd and isisd have the ability to advertise a
default route to their peers only if one exists in the RIB. This
is what the "default-information originate" commands do when used
without the "always" parameter.

For that to work, these daemons use the ZEBRA_REDISTRIBUTE_DEFAULT_ADD
message to request default route information to zebra. The problem
is that this message didn't have an AFI parameter, so a default route
from any address-family would satisfy the requests from both daemons
(e.g. ::/0 would trigger ospfd to advertise a default route to its
peers, and 0.0.0.0/0 would trigger isisd to advertise a default route
to its IPv6 peers).

Fix this by adding an AFI parameter to the
ZEBRA_REDISTRIBUTE_DEFAULT_{ADD,DELETE} messages and making the
corresponding code changes.

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