当viewController中只有一个scrollView时，点击statusBar，该scrollView就会滚动到顶部，但当viewController中有多个scrollView时，这个功能就失效了。
为什么呢？UIScrollView有个属性 ，叫scrollsToTop，看下官方注解：
“When the user taps the status bar, the scroll view beneath the touch which is closest to the status bar will be scrolled to top, but only if its `scrollsToTop` property is YES, its delegate does not return NO from `shouldScrollViewScrollToTop`, and it is not already at the top.
On iPhone, we execute this gesture only if there's one on-screen scroll view with `scrollsToTop` == YES. If more than one is found, none will be scrolled.”
@property (nonatomic) BOOL scrollsToTop __TVOS_PROHIBITED; // default is YES.
可以看到，点击statusBar时如果发现有多个scrollView时就不会有滚动效果了。
解决办法很简单，把需要有滚动效果的scrollView的scrollsToTop属性设为YES，其他的设为NO，也就是说同一时间内只能让一个scrollView的scrollsToTop属性为YES。
