Minimal modification for single threaded PRD to track association with MT scheduler.
requested to merge goetz/athena:PRDAssociation_master_minimal_migration_for_single_threaded_MTscheduler into master
The association map is stored in storegate for cases in which the PRD association is shared across multiple algorithms. The PRD_AssociationTool is still used for the cases in which the PRD association is shared between multiple tools but which are all related to a single algorithm instance. Thus, the PRD_AssociationTool still has to be public for tha latter cases. The current configuration does not ensure that tool instances are confined to single algorithms. Thus, in case of more than one thread, different algorithms may still operate concurrently on the same internal association map, which can be mitigated by configuration changes (to be done).
This addresses part of ATLASRECTS-5005