selftests/bpf: Add nolisten for network_helper_opts

This patch adds a struct member "nolisten" for network_helper_opts,
which is used to control whether to invoke listen() or not in
start_server_addr().

Also print out a warning if backlog is set for a type not support
listen for connections.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>