title: CompletitionService: poll timeout without reset it every time?
body: <p>I have a set of task which must be completed within a certain time, interrupt them otherwise. In particular uploads the same file on different Servers through <code>FTPClient</code> class. </p>
  
  <p>I thought that the <code>CompletionService</code> was the best solution for my problem, but the only problem is that the timeout used in <code>poll</code> is renewed at every element returned by the callable task, am I right? Sorry if I'm not, it's the first time that I use this mechanism.</p>
  
  <p>Anyway, this is not what I'm looking for because I want to set an upper bound for the completion of <strong>all</strong> the submitted task, not an upper bound for the next task completed!</p>
  
  <p>There is any solution/workaround for this problem? </p>