bpf, selftests: use :: 1 for localhost in tcp_server.py

Using localhost requires the host to have a /etc/hosts file with that
specific line in it. By default my dev box did not, they used
ip6-localhost, so the test was failing. To fix remove the need for any
/etc/hosts and use ::1.

I could just add the line, but this seems easier.

Signed-off-by: John Fastabend <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Song Liu <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/159594714197.21431.10113693935099326445.stgit@john-Precision-5820-Tower

tools/testing/selftests/bpf/tcp_client.py

···
 # create active socket
 sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
 try:
-    sock.connect(('localhost', serverPort))
+    sock.connect(('::1', serverPort))
 except socket.error as e:
     sys.exit(1)
 

tools/testing/selftests/bpf/tcp_server.py

···
 # create passive socket
 serverSocket = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
 
-try: serverSocket.bind(('localhost', 0))
+try: serverSocket.bind(('::1', 0))
 except socket.error as msg:
     print('bind fails: ' + str(msg))
 

tools/testing/selftests/bpf/test_netcnt.c

···
 	}
 
 	if (system("which ping6 &>/dev/null") == 0)
-		assert(!system("ping6 localhost -c 10000 -f -q > /dev/null"));
+		assert(!system("ping6 ::1 -c 10000 -f -q > /dev/null"));
 	else
-		assert(!system("ping -6 localhost -c 10000 -f -q > /dev/null"));
+		assert(!system("ping -6 ::1 -c 10000 -f -q > /dev/null"));
 
 	if (bpf_prog_query(cgroup_fd, BPF_CGROUP_INET_EGRESS, 0, NULL, NULL,
 			   &prog_cnt)) {