console: fix a bug in interactive readline usage

Spurious wakeups are possible in console, that makes readline
think that there are some data on stdin. Waked up readline
returns garbage instead of string, that crashes a server on
assertion in Lua.

Closes #3343

src/box/lua/console.c

@@ -221,8 +221,9 @@ lbox_console_readline(struct lua_State *L)
 	 */
 	rl_callback_handler_install(prompt, console_push_line);
 	top = lua_gettop(L);
-	while (top == lua_gettop(L) &&
-	       coio_wait(STDIN_FILENO, COIO_READ, TIMEOUT_INFINITY)) {
+	while (top == lua_gettop(L)) {
+		while (coio_wait(STDIN_FILENO, COIO_READ,
+				 TIMEOUT_INFINITY) == 0);
 
 		rl_callback_read_char();
 	}