fix(example): add installation of python-etcd in Pytorch example (kubeflow#2064)

Signed-off-by: champon1020 <[email protected]>

Author: champon1020

examples/pytorch/elastic/imagenet/Dockerfile

@@ -10,6 +10,9 @@ WORKDIR /workspace
 RUN apt-get -q update && apt-get -q install -y wget unzip
 RUN wget -q http://cs231n.stanford.edu/tiny-imagenet-200.zip && unzip -q tiny-imagenet-200.zip -d data && rm tiny-imagenet-200.zip
 
+# install dependent library
+RUN pip install --upgrade pip && pip install python-etcd
+
 COPY examples/pytorch/elastic/imagenet/ ./examples
 
 USER root