tmf: Add some unit tests to the ITmfStatistics

tmf: Add some unit tests to the ITmfStatistics

Also fixed some bugs that those tests exposed:
- Time ranges are now inclusive (both at the beginning and end)
  for all implementations.
- All methods in TmfStateStatistics will now wait for the history
  construction to be complete, so hopefully no more hundreds of
  AttributeNotFoundException's.
- State system queries at the end time should now work correctly
  (the work-around was removed).
- A time range beginning at the trace's start time should now
  return the correct values. I couldn't test with the edge case
  where you have more than 1 event exactly at the start time, but
  I assume it should work correctly too.

Change-Id: Ia4268eeb1c04033a41b4e8ea011a6007bc90187e
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/8463
Tested-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
IP-Clean: Patrick Tasse <patrick.tasse@gmail.com>