title: Extra 20px Top Inset UIScrollView Issue
body: <p>Questions regarding this issues has been asked. I tried everything and couldn't fix my problem. I struggled for 2 hours and now i am posting this here.</p>
  
  <p>Issue: UIScrollView's top contentInset has always 20px extra space.</p>
  
  <p>I have viewcontroller xib, not storyboard.</p>
  
  <p>First, related question and its solution on stackoverflow assumes that UIScrollView is the root view of UIViewController. But my scrollview is not root view and hence that why maybe </p>
  
  <blockquote>
    <p>self.automaticallyAdjustsScrollViewInsets = NO;</p>
  </blockquote>
  
  <p>is not working</p>
  
  <ul>
  <li>I have one HeaderView with leadingspace(0, superview), trailing space(0, super view), top space(0, superview)
  and fixed height.</li>
  <li>Below header view is scrollview with leading space(0, superview),
  trailing space(0, superview), bottom space(0, superview) and vertical
  space(0, header view)</li>
  <li>There is a view inside the scrollview for contents. This view has
  leading(0), trailing(0), bottom(0) and top(0) space to scrollview.</li>
  </ul>
  
  <p>Here is the screenshot of that extra 20 px top inset. Extra 20px is the black area between white line and light gray content of UIScrollView I am unable to get this fixed.
  <img src="https://i.stack.imgur.com/zDEie.png" alt="enter image description here"></p>
  
  <p>Am i doing something wrong? Autolayout constraints seems fine.</p>