selftests/bpf: Add opts argument for __start_server

This patch adds network_helper_opts parameter for __start_server()
instead of "int protocol" and "int timeout_ms". This not only reduces
the number of parameters, but also makes it more flexible.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/127d2f0929980b41f757dcfebe1b667e6bfb43f1.1714014697.git.tanggeliang@kylinos.cn


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>