Fix various problems with hpvm-c benchmarks

...-c/benchmarks/alexnet2_cifar10/alexnet2_cifar10_cudnn.cpp

...vm-c/benchmarks/alexnet_cifar10/alexnet_cifar10_cudnn.cpp

...-c/benchmarks/alexnet_imagenet/alexnet_imagenet_cudnn.cpp

...marks/hpvm-c/benchmarks/lenet_mnist/lenet_mnist_cudnn.cpp

.../benchmarks/mobilenet_cifar10/mobilenet_cifar10_cudnn.cpp

...-c/benchmarks/resnet18_cifar10/resnet18_cifar10_cudnn.cpp

.../benchmarks/resnet50_imagenet/resnet50_imagenet_cudnn.cpp

...s/hpvm-c/benchmarks/vgg16_cifar10/vgg16_cifar10_cudnn.cpp

...hpvm-c/benchmarks/vgg16_cifar100/vgg16_cifar100_cudnn.cpp

...hpvm-c/benchmarks/vgg16_imagenet/vgg16_imagenet_cudnn.cpp