switch back to use associator for track validation

Fix problem in track validation which was introduced with my recent PR (validation worked ok only for generalTracks).
Go back to use of associators on the fly for track validation.
Main speedup for trackingParticleRecoTrackAsssociation will still be there.
Doing PR for 71Xs, 70X and 62XSLHC.
This one for 71X.