Added code to update scrollIndicatorInsets when updating contentInset.

Not sure if this works with scrollIndicator insets that were set by the user, but I was having issues where the contentInsets and scrollIndicatorInsets were not the same. In my I have a root UIView with a single UIScrollView as a child and a single UITextView as a child of the scroll view. the UITextView is setup with disabled scrolling. This fix works perfectly for my situation.