remove hard-coded paths in Sherpa tarCreator
One of the sub-steps of the Sherpa tarCreator uses Python to create a bash script that sets up cvmfs-based library paths to the various dependencies used by the OpenMPI-enabled version of Sherpa on cvmfs, which we use for process integrations. These paths are currently hardcoded. This change set is to remove the hardcoded paths in favour of environment-variable-based path setting.