FIX drop obsolete CURAND reset for CUDA 6.5 compatibility

Drop the legacy CURAND initialization steps; these are unnecessary and
cause dramatic slowdowns for CUDA 6.5. This does no harm for K20 usage
counter to the note at least for CUDA 6.5 and 5.0.
Merge pull request #984 from shelhamer/drop-curand-reset

Drop obsolete CURAND reset for CUDA 6.5 compatibility