Add directly-connected routes for IPv4 as well.

A normal Android system will have directly-connected routes for
on-link prefixes in the per-interface tables for both IPv4 and
IPv6. The tests creates these routes for IPv6 (if they're not
already created by the autoconf sysctl), but doesn't create them
for IPv4. Create them for IPv4 as well.

Also, move the code that creates the unreachable rule so it
runs before we create any other rule. Previously, the routing
setup code relied for correctness on the fact that the
unreachable rule was created after routes were created. Creating
the unreachable rule first ensures that the routes are correct in
themselves.

Change-Id: I33667b4642e8dd9299bd6dc5a404e6e71e1be163