tools/bpf: fix test_sock and test_sock_addr.sh failure

tools/bpf: fix test_sock and test_sock_addr.sh failure

The bpf selftests test_sock and test_sock_addr.sh failed
in my test machine. The failure looks like:
    $ ./test_sock
    Test case: bind4 load with invalid access: src_ip6 .. [PASS]
    Test case: bind4 load with invalid access: mark .. [PASS]
    Test case: bind6 load with invalid access: src_ip4 .. [PASS]
    Test case: sock_create load with invalid access: src_port .. [PASS]
    Test case: sock_create load w/o expected_attach_type (compat mode) .. [FAIL]
    Test case: sock_create load w/ expected_attach_type .. [FAIL]
    Test case: attach type mismatch bind4 vs bind6 .. [FAIL]
    ...
    Summary: 4 PASSED, 12 FAILED
    $ ./test_sock_addr.sh
    Wait for testing IPv4/IPv6 to become available .....
    ERROR: Timeout waiting for test IP to become available.

In test_sock, bpf program loads failed due to hitting memlock limits.
In test_sock_addr.sh, my test machine is a ipv6 only test box and using
"ping" without specifying address family for an ipv6 address does not work.

This patch fixed the issue by including header bpf_rlimit.h in test_sock.c
and test_sock_addr.c, and specifying address family for ping command.

Cc: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>