title: Does onCompleted works with useMutation?
body: <p>I am using useMutation hook in react project. The mutation runs successfully but it's not reaching onCompleted afterwards. </p>
  
  <p>I have set notifyOnNetworkStatusChange to true in the mutation but that doesn't seem to help.</p>
  
  <pre><code>const [createUser] = useMutation(SIGNUP_MUTATION);
  
  createUser({
    variables: {
       firstname,
       lastname,
       email
    },
    notifyOnNetworkStatusChange: true,
    onCompleted: (data) =&gt; {
       // not called
       confirm(data);
    }
  });
  </code></pre>