internal diagnostic timing routines are skewed if processes call MPI_Finalize() at different times

Darshan includes a feature that will display internal diagnostic timing information if the DARSHAN_INTERNAL_TIMING environment variable is set. However, the mechanism used to collect timing information assumes that all processes have called MPI_Finalize() simultaneously. If this is not the case, then the diagnostic information will erroneously attribute too much time to Darshan while it waits on the other processes to synchronize.