pulse-server: alsa safely make native socket

Only make the native socket when it's not there or when it appears
dead when we can't seem to connect to it.

- When the socket is not found, we take it.
- When an existing pulseaudio is running we won't unlink and take
  over the socket because we can connect to it
- When a crashed pulseaudio leaves a stale socket, we fail to
  connect and then we unlink and take over.