Rework run_digi test

test_run_digi should be split into 2 phases:

1. test_run_raw generates data based on test dataset /cvmfs/bmn.jinr.ru/ci/mpd_run_Top_7883_ev0_p0.data
2. test_run_digi runs reconstruction on the data generated during the first stage.

This test can now be run right after the build, since it doesn't depend on test_run_reco anymore.