Don't access freed memory in emacsclient

Don't access freed memory in emacsclient

* emacsclient.c (socket_name): Add const.
(get_server_config): Add parameter config_file, use it instead of
global server_file.
(set_tcp_socket): Add parameter local_server_file, pass it down to
get_server_config.
(set_local_socket): Add parameter local_socket_name, use it
instead of global socket_name.
(set_socket): Adjust calls to set_local_socket and set_tcp_socket.
Don't clobber global server_file or socket_name.
(main): No longer reset server_file or socket_name.