selftests: add ping test with ping_group_range tuned

selftests: add ping test with ping_group_range tuned

The 'ping' utility is able to manage two kind of sockets (raw or icmp),
depending on the sysctl ping_group_range. By default, ping_group_range is
set to '1 0', which forces ping to use an ip raw socket.

Let's replay the ping tests by allowing 'ping' to use the ip icmp socket.
After the previous patch, ipv4 tests results are the same with both kinds
of socket. For ipv6, there are a lot a new failures (the previous patch
fixes only two cases).

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>