server: split file descriptors in in/out fd's

pipes have different fd's for in/out. This makes the
code more orthogonal and prepares for adding pipes.

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

src/server/tcl_server.c

@@ -58,6 +58,7 @@ int tcl_output(struct connection *connection, const void *data, ssize_t len)
 		return ERROR_SERVER_REMOTE_CLOSED;
 
 	wlen = write_socket(connection->fd, data, len);
+
 	if (wlen == len)
 		return ERROR_OK;