lisp/server.el: Use just one way to pass the Emacs PID to emacsclient.

lisp/server.el: Use just one way to pass the Emacs PID to emacsclient.

* lib-src/emacsclient.c (get_server_config): Don't read Emacs pid from
  the authentication file.

* lisp/server.el (server-start): Don't write pid to the authentication file.
  (server-create-tty-frame): Don't send pid.
  (server-process-filter): Send pid at the start of every connection.