Add a test for issue 100 in DaVinciTests

Closes #100 (closed).

The test is a shorter version of the original script focusing only on what was giving trouble.

DaVinciTests/python/DaVinciTests/mc/option_davinci-issue-100_multiple_bkgcat_mc-truth.py

@@ -15,8 +15,7 @@ of the `MCTruthAndBkgCat` helper in Analysis's `Phys/DaVinciMCTools` package,
 traced back to a bug in one of the tools internally called.
 The test ensures that several instances of `MCTruthAndBkgCat`
 can be used in the same script to produce several ntuples.
-rst_running: lbexec DaVinciTests.mc.option_davinci-issue-100_multiple_bkgcat_mc-truth:main 
-"$DAVINCITESTSROOT/python/DaVinciTests/mc/option_davinci-issue-100_multiple_bkgcat_mc-truth.yaml"
+rst_running: lbexec DaVinciTests.mc.option_davinci-issue-100_multiple_bkgcat_mc-truth:alg_config "$DAVINCITESTSROOT/python/DaVinciTests/mc/option_davinci-issue-100_multiple_bkgcat_mc-truth.yaml"
 rst_yaml: ../DaVinciTests/python/DaVinciTests/mc/option_davinci-issue-100_multiple_bkgcat_mc-truth.yaml
 """
 from PyConf.reading import get_particles