selftests: fcnal: Test SO_DONTROUTE on raw and ping sockets.

Use ping -r to test the kernel behaviour with raw and ping sockets
having the SO_DONTROUTE option.

Since ipv4_ping_novrf() is called with different values of
net.ipv4.ping_group_range, then it tests both raw and ping sockets
(ping uses ping sockets if its user ID belongs to ping_group_range
and raw sockets otherwise).

With both socket types, sending packets to a neighbour (on link) host,
should work. When the host is behind a router, sending should fail.

Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>