MINOR: protocol: do not call proto->bind_all() anymore

MINOR: protocol: do not call proto->bind_all() anymore

All protocols only iterate over their own listeners list and start
the listeners using a direct call to their ->bind() function. This
code duplication doesn't make sense and prevents us from centralizing
the startup error handling. Worse, it's not even symmetric because
there's an unbind_all_listeners() function common to all protocols
without any equivalent for binding. Let's start by directly calling
each protocol's bind() function from protocol_bind_all().