ATLASRECTS-4971: Use SlotSpecificObj to support concurrency.

To mimic SCT_ByteStreamErrorsTool in SCT_ConditionsTools, I put all the mutables inside a SlotSpecificObj struct and split functions accessing them into two parts, one public that acquires a mutex lock and calls the private function that does the actual work within the given Event context. I assume SlotSpecificObj needs to be protected by a mutex, so I left the counters intact as (non-atomic) integers.

RunTier0Tests.py runs successfully under master,2019-10-25T2129. See the attached log file, RunTier0Tests.log