image: Set dragging pointer on button press, not first motion

We want feedback that we're starting to drag when we press the button
not when we later start dragging the image.

clients/image.c

@@ -240,14 +240,14 @@ button_handler(struct widget *widget,
 	       void *data)
 {
 	struct image *image = data;
-	bool was_pressed;
 
 	if (button == BTN_LEFT) {
-		was_pressed = image->button_pressed;
 		image->button_pressed =
 			state == WL_POINTER_BUTTON_STATE_PRESSED;
 
-		if (!image->button_pressed && was_pressed)
+		if (state == WL_POINTER_BUTTON_STATE_PRESSED)
+			input_set_pointer_image(input, CURSOR_DRAGGING);
+		else
 			input_set_pointer_image(input, CURSOR_LEFT_PTR);
 	}
 }