selftests/bpf: Drop make_socket in sk_lookup

selftests/bpf: Drop make_socket in sk_lookup

This patch uses the public network helers client_socket() + make_sockaddr()
in sk_lookup.c to create the client socket, set the timeout sockopts, and
make the connecting address. The local defined function make_socket()
can be dropped then.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/588771977ac48c27f73526d8421a84b91d7cf218.1721475357.git.tanggeliang@kylinos.cn
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>