attempt to fix an intermittent failure in TestDetectionsPlot

[bspratt]

No description provided.

[nickshulman]

I wonder if @rita-gwen has any ideas about how this could be fixed.
In theory that DetectionPlotData.GetDataCache().Status == DetectionPlotData.DetectionDataCache.CacheStatus.idle is supposed to wait until the cache has no more work to do, so it might be that something in there is not working the way that we would expect.

[bspratt]

I wonder if @rita-gwen has any ideas about how this could be fixed. In theory that DetectionPlotData.GetDataCache().Status == DetectionPlotData.DetectionDataCache.CacheStatus.idle is supposed to wait until the cache has no more work to do, so it might be that something in there is not working the way that we would expect.

Yeah, I was thinking that we might be overrunning that - asking for its status before its even aware that there's work to be done