make Trigger Daemon sleep correctly when one-time triggers exist

Summary:
Trigger daemon is trying to find the next event to invoke before sleeping, but the query includes already-elapsed triggers.
It then tries to sleep for 0 seconds.

Test Plan:
On a new instance, schedule a single trigger of type `PhabricatorOneTimeTriggerClock` to a very near time.

Use top to see trigger daemon not going to 100% CPU once the event has elapsed.

Reviewers: #blessed_reviewers, epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15750

src/infrastructure/daemon/workers/PhabricatorTriggerDaemon.php

@@ -261,7 +261,7 @@ final class PhabricatorTriggerDaemon
    * Get the number of seconds to sleep for before starting the next scheduling
    * phase.
    *
-   * If no events are scheduled soon, we'll sleep for 60 seconds. Otherwise,
+   * If no events are scheduled soon, we'll sleep briefly. Otherwise,
    * we'll sleep until the next scheduled event.
    *
    * @return int Number of seconds to sleep for.
@@ -272,6 +272,7 @@ final class PhabricatorTriggerDaemon
     $next_triggers = id(new PhabricatorWorkerTriggerQuery())
       ->setViewer($this->getViewer())
       ->setOrder(PhabricatorWorkerTriggerQuery::ORDER_EXECUTION)
+      ->withNextEventBetween(0, null)
       ->setLimit(1)
       ->needEvents(true)
       ->execute();