paranoid about this, and only remove the specified file if connect says
the connection was refused and stat says the file is a socket.
Also dtach -A now only tries to create the socket if the connection was
refused or the socket did not exist, instead of on any random error as
before.
exiting silently.
Also make sure the master process waits until the client attaches when using
the -A and -c modes, so that the error message has a chance of being seen.