Fix top level menu lingering when submenu opens.

We should be calling close(false), not dismiss(), when the submenu is
opened.

This change brings the code closer to what it was before the prior
change to StandardMenuPopup, but preserves the ondismiss behavior we
want for popup menus. The net change so far is that StandardMenuPopup,
not MenuBuilder#performItemAction, handles closing the top level menu
when a submenu is opened. But nonetheless, the onDismiss is not called
when a submenu is opened; only when an actual real "dismiss" occurs.

Bug: 28001958
Change-Id: Ia0f89f8fd4bc5494f6a048c993792adfe42d88ec