title: JPA EntitiyManager - find Parent by id does not return instance with previously added children
body: <p>Suppose we have standard one-to-many relationship between Parent and Child objects. In other words, one Parent holds list of Child objects. </p>
  
  <p>Mapping is standard... Ids in both classes are annotated with @GeneratedValue(strategy = GenerationType.IDENTITY)... There are all getters and setters... </p>
  
  <pre><code>Parent{
      ....
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "parent")
      Collection&lt;Child&gt; children;
      ....
  }
  
  Child{
      ...
      @ManyToOne(optional = false)
      Parent parent;
      ...
  }
  </code></pre>
  
  <p>Child object is the owning side of relation. When I save owning Child object, and after that fetch Parent object, I expect to get previously saved Child within parent. More precise, when I execute this code: </p>
  
  <pre><code>EntityManager em... 
  Parent p = new Parent();
  em.persist(p);
  em.flush();
  
  Child c = new Child();
  c.setParent(p);
  em.persist(c);
  em.flush();
  
  Parent savedParent = em.find(Parent.class, p.getId());
  savedParent.getChildren().size(); //this call returns 0 instead of 1 (why?)
  </code></pre>
  
  <p>...I expect that savedParent has in collection previously saved one child. But, for some reason, this does not work. Any ideas?</p>