Dashboard - Bump alert limits for group_report.
Dashboard - Bump alert limits for group_report.

Previously we queried for up to 2000 alerts, and then only displayed 500. Bumping this up as a temp solution to
alerts with large ranges not getting displayed. This will still fail to show all the alerts since it's not a
true overlap test, but will at least show more of them until we get to the overlap query itself.

BUG=chromium:755661

Review-Url: https://codereview.chromium.org/3001783002

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult