Docker: Install Python packages 'requests' and 'Pillow' (#3495)

Needed for:

- https://github.com/dmlc/tvm/blob/287078c33db85d4f312d8d2457a064442d9d18c3/tutorials/frontend/deploy_model_on_android.py#L30
- https://github.com/dmlc/tvm/blob/287078c33db85d4f312d8d2457a064442d9d18c3/tutorials/frontend/deploy_model_on_android.py#L37
- https://github.com/dmlc/tvm/blob/287078c33db85d4f312d8d2457a064442d9d18c3/python/tvm/contrib/download.py#L58

docker/install/ubuntu_install_python_package.sh

@@ -22,4 +22,4 @@ set -o pipefail
 
 # install libraries for python package on ubuntu
 pip2 install nose pylint==1.9.4 six numpy nose-timer cython decorator scipy tornado typing antlr4-python2-runtime attrs
-pip3 install nose pylint==1.9.4 six numpy nose-timer cython decorator scipy tornado typed_ast pytest mypy orderedset antlr4-python3-runtime attrs
+pip3 install nose pylint==1.9.4 six numpy nose-timer cython decorator scipy tornado typed_ast pytest mypy orderedset antlr4-python3-runtime attrs requests Pillow