selftests/bpf: Drop make_client in sk_lookup

selftests/bpf: Drop make_client in sk_lookup

This patch uses the new helper connect_to_addr_str() in sk_lookup.c to
create the client socket and connect to the server, instead of using local
defined function make_client(). This local function can be dropped then.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/058199d7ab46802249dae066ca22c98f6be508ee.1721475357.git.tanggeliang@kylinos.cn
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>