tests/netlink_inet_diag.c: use libtests
tests/netlink_inet_diag.c: use libtests

* tests/netlink_inet_diag.c (send_query, check_responses, main):
Use perror_msg_and_skip.

cuviper/strace,cuviper/strace,cuviper/strace,cuviper/strace,Saruta/strace,cuviper/strace,Saruta/strace,Saruta/strace,Saruta/strace,Saruta/strace