restore prior Future.get behavior

In Finagle 5, Future.get would return a Throw(TimeoutException) for
timeouts:

  def get(timeout: Duration): Try[A] =
    ivar(timeout) getOrElse {
      Throw(new TimeoutException(timeout.toString))
    }

In Finagle 6, this behavior changed so that TimeoutException is
thrown instead. This is caused by Await.ready not being within the
try block.

Deprecated functions should not change beavior. This commit restores
that behavior.