Fix image name

Image name wasn't consistent.

Author: Dan

advanced_functionality/tensorflow_bring_your_own/tensorflow_bring_your_own.ipynb

@@ -430,7 +430,7 @@
     "estimator = Estimator(role=role,\n",
     "                      train_instance_count=1,\n",
     "                      train_instance_type=instance_type,\n",
-    "                      image_name='tensorflow_cifar10_example:latest',\n",
+    "                      image_name='tensorflow-cifar10-example:latest',\n",
     "                      hyperparameters=hyperparameters)\n",
     "\n",
     "estimator.fit('file:///tmp/cifar-10-data')\n",