Make TRT data preparation reentrant
Make TRT reentrant. The code that blocked this is legacy code required for the Run-2 steering.
Tested locally with 8 threads + 100 events - identical results.
Although we don't plan to run multi-threaded at P1 there is a slight performance improvement by passing EventContext down rather than calling currentContext(). So it's probably still worth doing.
Edited by Stewart Martin-Haugh