title: Entity manager's delete child is not detaching child from parent
body: <p>I have a parent entity and a one to many reference of <code>Set&lt;Child&gt;</code> in this parent entity… 
  on using entity manager's(being injected in my <code>DAO</code> as say "em") delete as <code>em.delete(child)</code> is not deleting its reference from my parent's list…</p>
  
  <p>like after debugging <code>parent.getChildren()</code>, I can still find that child that has been deleted in the parent's children list…</p>
  
  <p>How do i detach this child from parent's list??</p>