title: Change layout_scrollFlags programmatically in CollapsingToolbarLayout
body: <p>I have the following CollapsingToolbarLayout tag in my xml:</p>
  
  <pre><code>&lt;android.support.design.widget.CollapsingToolbarLayout
      android:id="@+id/collapsingToolbarLayout"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      app:contentScrim="?attr/colorPrimary"
      app:expandedTitleMarginStart="@dimen/expanded_toolbar_title_margin_start"
      app:layout_scrollFlags="exitUntilCollapsed"&gt;
  </code></pre>
  
  <p>I would like to change the scrollFlags value programmatically (run time) -  specifically, toggle the scrollable flag. Is it possible?</p>