Don't add MC truth tools for data events

This MR is needed as a follow-up on !24994 (merged). The MC truth tools were set up for data as well as MC and caused an error in the ATLAS release tester for the derivation framework here (search output for mcChannelNumber).

The newly introduced check makes makes sure that the tools are only set up for MC. To test these changes, I ran on lxplus

setupATLAS
lsetup git
lsetup cmake
asetup AthDerivation,21.2,r2019-07-25

cmake -DATLAS_PACKAGE_FILTER_FILE=../package_filters.txt ../athena/Projects/WorkDir/
make
source x86_64-centos7-gcc62-opt/setup.sh

../athena/PhysicsAnalysis/DerivationFramework/DerivationFrameworkART/test/test_data18EXOT8.sh

The output of the job looks good to me (line 6949, where the error was in the previous log; summary of message in the end does not show any errors). Please confirm that I ran the job correctly and that the output looks fine, @boeriu.

Konstantin