Updates related to the app's name and its docker file

Change-Id: If24c36cd8460be20978236b95547f6a6e03fd84a
diff --git a/docker/Dockerfile b/docker/Dockerfile
index dee64fa..5641eee 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -3,12 +3,11 @@
 # SPDX-FileCopyrightText: 2020-present Open Networking Foundation <info@opennetworking.org>
 # SPDX-License-Identifier: Apache-2.0
 #
-FROM ubuntu:18.04
-ADD . /
-RUN set -xe \
-    && apt-get update -y \
-    && apt-get install -y python3-pip
+FROM python:3.6-slim-buster
+WORKDIR /app
+COPY requirements.txt requirements.txt
 RUN pip3 install --upgrade pip
 RUN pip3 install -r requirements.txt
+COPY . .
 EXPOSE 3333
-ENTRYPOINT [ "python3", "./app.py"]
+ENTRYPOINT [ "python3", "./network-diag-app.py"]