Add site-packages into the PATH environment variable. (#2115)

* Add site-packages in the PATH environment variable too

* Do some rephrase

* Remove dist-packages.

Author: brightcoder01

elasticdl_client/api.py

@@ -50,7 +50,7 @@ def init_zoo(args):
  --extra-index-url={{ EXTRA_PYPI_INDEX }}
 
 RUN pip install elasticdl --extra-index-url={{ EXTRA_PYPI_INDEX }}
-ENV PATH /usr/local/lib/python3.6/dist-packages/elasticdl/go/bin:$PATH
+ENV PATH /usr/local/lib/python3.6/site-packages/elasticdl/go/bin:$PATH
 
 COPY . /model_zoo
 RUN pip install -r /model_zoo/requirements.txt\