Comment 4 for bug 1285215

I think this happens when you have a lingering socket file from the previous server:
    /tmp/mir_socket
or wherever it is.

Mir (server) doesn't contain any smarts to test the validity of existing socket files. I'm assuming the old server is dead. In that case we'd need a way to probe if a socket file is presently opened by any other (server) process. If not then delete it and try again.