Add a --reuse option to test existing paths

[Josh Stone]

I have an idea for an option something like "--reuse", which will try to preserve some existing socket path given by "-a". The idea is to just try to connect() to that path, and if that works assume all is well, just report that path and quit. If connect fails, remove the existing path and create it anew. (But as a safety check, don't remove it if it's not a socket type.)