Change check_vectors task to skip if requested end is after now, instead of requested start

Fix a bug where the check_vectors task would try to run even if the end of the requested time was in the future. This would then ask for a StateVector check with data that didn't yet exist.

Should help address #614 (closed), though I don't think it fixes it completely (since there appear to be events where this failure happens even for non-EW events, which occur in the past).

gwcelery/tasks/detchar.py

@@ -419,7 +419,7 @@ def check_vectors(event, graceid, start, end):
 
     """
     # Skip early warning events (ie queries for times before now)
-    if start > Time.now().gps:
+    if end > Time.now().gps:
         log.info("Skipping detchar checks because %s is in the future",
                  event['graceid'])
         return event