CNTK single gpu doesn't run because of node count comparison. (#79)

* Bugfix: cntk single gpu is never ran because of node count comparison.

For single node, single gpu scenario, $AZ_BATCH_HOST_LIST has a single
IP, and hence the count of nodes will be 1.

* Updating condition.

recipes/CNTK-GPU-OpenMPI/docker/run_convnet_mnist_gpu.sh

@@ -17,7 +17,7 @@ IFS=',' read -ra HOSTS <<< "$AZ_BATCH_HOST_LIST"
 nodes=${#HOSTS[@]}
 
 # special path for non-mpi job with single gpu
-if [ $nodes -eq 0 ] && [ $ngpus -eq 1 ]; then
+if [ $nodes -le 1 ] && [ $ngpus -eq 1 ]; then
     echo "running cntk in single node + single gpu mode"
     # set cntk file
     cntkfile=/cntk/Examples/Image/Classification/ConvNet/BrainScript/ConvNet_MNIST.cntk