Add the fib6_flags and fib6_type to fib6_result. Update the lookup helpers
to set them and update post fib lookup users to use the version from the
result.

This allows nexthop objects to have blackhole nexthop.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>