Add new test for checking results of AOD merge
Add a new test to check that AODMerge doesn't change the AOD content.
In future an option may be to add this check to one of the other aod merge tests, but the inputs there are too old for this check to work (and we haven't yet decided what to do about updating reference files on cvmfs).
It could also be added to one of the other tests running q445, but I though it better to avoid over-complicating them.