Added max_boxes for yolo v3

AlexeyAB

2018-03-30 35cc0aaa15b991b348cc8d9623eed5d4f8a1e435

 src/network_kernels.cu

@@ -121,7 +121,7 @@
   }
#endif
    forward_network_gpu(net, state);
   cudaStreamSynchronize(get_cuda_stream());
   //cudaStreamSynchronize(get_cuda_stream());
    backward_network_gpu(net, state);
}