Fix const correctness. Add const to estimateNumberOfParticles and estimatePositions of TruthClusterizationFactory

Fix const correctness. Add const to estimateNumberOfParticles and estimatePositions.

http://atlas-computing.web.cern.ch/atlas-computing/links/distDirectory/gitwww/UPGRADE_INTEGRATIONWebArea/nicos_web_areaconstmaster_Athena_x86_64slc6gcc62opt64BS6G62AthenaOpt/NICOS_Log_2019-01-26T0957/InnerDetector_InDetRecTools_SiClusterizationTool.html

This can be checked by

cmake -DATLAS_PACKAGE_FILTER_FILE=../package_filters.txt -DATLAS_ALLOW_TOOLHANDLE_NONCONSTNESS=OFF ../athena/Projects/WorkDir
make