Refactor: tools: Improve error handling on connection failure.

• Rename handle_connection_failures to clean_up_if_connection_failure, which makes it more clear exactly what it does.
• Pass the rc value through pcmk_rc2exitc to get the value that clean_up expects, making this no longer the caller's problem.
• Don't check rc before calling clean_up_if_connection_failure since that's the very first thing it does. This function is safe to be unconditionally called.