title: Watches never trigger in FoundationDB
body: <p>I playing around with watches functionality and struggling to get it work. 
  The problem is that watch never fires, it simply not react to changes that I make for key in other transactions.</p>
  
  <pre><code>val key = new Tuple().add("watch-test").pack()
  val watchExecuted = db.runAsync(tr =&gt; {
    tr.set(key, new Tuple().add(1).pack())
    tr.watch(key)
  })
  
  Thread.sleep(5000) // ensure that watch applied
  
  db.run(tr =&gt; {
    tr.set(key, new Tuple().add(2).pack())
  })
  
  watchExecuted.get() // never finish
  </code></pre>
  
  <p>Is anybody have any idea why watches do not react on changes as it supposed to do?</p>