events could be duplicated between real time/long polling event calls

[mblackstock]

Reviewed the code - I think this is a bug, but we need a test.

The logic for getting real time events is:

    List<Event> events = eventDao.getEvents(t, queryParams, filter);

    if (events.size() > 0)
        return events;

    return realTimeEventService.getEvents(a.getId(), t, waitTime, filter);

We can get the same event twice if the database stores an event and the queryParams includes it. The first call could call realTimeEventService.getEvents(), allocating a real time buffer. The next call to get events could get the events from the dao. The third next call could get the same event from the real time queue since the buffer is allocated.

To fix, we should have a parameter to explicity say whether we want real time or historical events?