Chronos should set a non-default filter when declining offers

[gkleiman]

Use case: As a cluster operator I would like to run many frameworks (possibly multiple Chronos instances) on the same Mesos cluster. I'd like to mitigate offer starvation; that is, schedulers with work to do should receive offers from the Mesos master.

From the SchedulerDriver documentation, Chronos can use both the overloaded definition of declineOffer to set filters:

  /**
   * Declines an offer in its entirety and applies the specified
   * filters on the resources (see mesos.proto for a description of
   * Filters). Note that this can be done at any time, it is not
   * necessary to do this within the {@link Scheduler#resourceOffers}
   * callback.
   *
   * @param offerId The ID of the offer to be declined.
   * @param filters The filters to set for any remaining resources.
   *
   * @return        The state of the driver after the call.
   *
   * @see OfferID
   * @see Filters
   * @see Status
   */
  Status declineOffer(OfferID offerId, Filters filters);

and clear them later on.

  /**
   * Removes all filters, previously set by the framework (via {@link
   * #launchTasks}). This enables the framework to receive offers
   * from those filtered slaves.
   *
   * @return    The state of the driver after the call.
   *
   * @see Status
   */
  Status reviveOffers();

Proposal: _When the task queue becomes empty, decline subsequent offers with a long timeout (say, max double value). When the task queue becomes non-empty, invoke reviveOffers.

NOTE: This issue is analogous to mesosphere/marathon#1931