Add reference comparison to pp_track_mva test

Add reference comparison to pp_track_mva test such that we have some test coverage/sensitivity to changes in the Kalman fit.

Also, fix BlockSkipper in ref_preprocessor (introduced with !339 (merged)).

After this is merged, Rec!1760 (merged) can be tested.

Depends on LHCb!2308 (merged)

added testing label

@mstahl we might need to commit platform-specific refs, so let's flag this with lhcb-head or lhcb-gaudi-head (it won't affect other tests)

added lhcb-head label

mentioned in merge request Rec!1760 (merged)

changed the description

• [2020-01-09 00:10] Validation started with lhcb-head#2477

resolved all threads

assigned to @rmatev and unassigned @mstahl

added 1 commit

• f2264a3c - Ensure that we keep lines sorted by not using set

Compare with previous version

added ci-test-triggered label

resolved all threads

approved this merge request

removed ci-test-triggered lhcb-head labels

unassigned @rmatev

merged

mentioned in commit e09922b3

mentioned in issue #128 (closed)

added hlt1 label