LPS-48432 Shopping portlet throws an error with a minimum order amount and a 0 quantity item at checkout

The pull request extends from https://github.com/hhuijser/liferay-portal/pull/2010.

The ShoppingUtil.meetsMinOrder()  method is not needed because the method only take effect once when the cart.jsp loaded. We should check the situation depending on the actual subtotal because we can change item's count in UI..

And the check also should only occur in cmd = 'checkout'. If alert("") execute, we also should change the param CMD and redirect for default value.

Thanks,
Hai