Start nvprof profiling at counter reset

When running in the NVIDIA profiler, to eliminate initial kernel
performance fluctuations, load balancing effects, as well as
initialization API calls from the traces, we now start the NVIDIA
profiler through the CUDA runtime API at the performance counter
resetting. This has an effect only if mdrun is started in nvprof with
profiling off.

Change-Id: Idfb3c86a96cb8b55cd874f641f4922b5517de6e3