Add CI test for upgrade
A recent merge request (!274 (merged)) broke the upgrade dumper, as reported by @tstreble. We should probably add some tests to prevent this in the future. Apparently this is a good sample to use
mc15_14TeV.600012.PhPy8EG_A14_ttbar_hdamp258p75_nonallhad.recon.AOD.e8185_s3695_s3700_r12714_tid25925560_00/AOD.25925560._000506.pool.root.1
Hopefully it's not too large: ideally we keep these these small so they are quick to run.