selftests/bpf: Drop __start_server in network_helpers

selftests/bpf: Drop __start_server in network_helpers

The helper start_server_addr() is a wrapper of __start_server(), the
only difference between them is __start_server() accepts a sockaddr type
address parameter, but start_server_addr() accepts a sockaddr_storage one.

This patch drops __start_server(), and updates the callers to invoke
start_server_addr() instead.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/31399df7cb957b7c233e79963b0aa0dc4278d273.1721475357.git.tanggeliang@kylinos.cn
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>