have realtime engine only search recent indexes

Elastic Recheck is really 2 things, real time searching, and bulk
offline categorization. While the bulk categorization needs to look
over the entire dataset, the real time portion is really deadline
oriented. So only cares about the last hour's worth of data. As such
we really don't need to search *all* the indexes in ES, but only
the most recent one (and possibly the one before that if we are near
rotation).

Implement this via a recent= parameter for our search feature. If set
to true then we specify the most recently logstash index. If it turns
out that we're within an hour of rotation, also search the one before
that.

Adjust all the queries the bot uses to be recent=True. This will
hopefully reduce the load generated by the bot on the ES cluster.

Change-Id: I0dfc295dd9b381acb67f192174edd6fdde06f24c

elastic_recheck/bot.py

@@ -196,7 +196,10 @@ class RecheckWatch(threading.Thread):
 
                 for job in event.failed_jobs:
                     job.bugs = set(classifier.classify(
-                        event.change, event.rev, job.build_short_uuid))
+                        event.change,
+                        event.rev,
+                        job.build_short_uuid,
+                        recent=True))
                 if not event.get_all_bugs():
                     self._read(event)
                 else: