title: patchValue with { emitEvent: false } triggers valueChanges on Angular 4 formgroup
body: <p>I have a formbuilder group and am listening for changes with valueChanges and triggering a save function followed by refresh function on the form:</p>
  
  <pre><code> this.ticketForm.valueChanges.debounceTime(1000).distinctUntilChanged()
   .subscribe(data =&gt; {
     this.saveTicket();
     this.refreshTicket();
   })
  </code></pre>
  
  <p>I am then reloading the form and repatching the data to form fields (and elsewhere on the page, particularly a change log) with patchValue, e.g.:</p>
  
  <pre><code>    this.ticketForm.patchValue(ticket, { emitEvent: false });
  </code></pre>
  
  <p>however, this causes an infinite loop of saves of the form despite emitEvent : false. </p>
  
  <p>Is this an Angular 4/Ionic 3 bug or a misunderstanding on my part?</p>