Update app to use envs for server info

Dockerfile

@@ -13,10 +13,5 @@ RUN pip install --no-cache-dir -r requirements.txt
 # Copy the client code into the container
 COPY ./app/ .
 
-# Define environment variable for the server host
-# This will be set by the Makefile when running the container
-ENV SERVER_HOST=localhost
-
 # Run client.py when the container launches
-# We use a list form of CMD to properly handle signals
 CMD ["python", "client.py"]