Re-sequence Dockerfile for quicker dev rebuilds

This is primarily a convenience for developers to improve iteration.

Change-Id: I7bfe7b6d37c128ef700a8a0e6656e7e139ad0582

Dockerfile

@@ -6,28 +6,33 @@ ENV DEBIAN_FRONTEND noninteractive
 ENV LANG=C.UTF-8
 ENV LC_ALL=C.UTF-8
 
-COPY requirements.txt /tmp/
-RUN pip3 install -r /tmp/requirements.txt
+EXPOSE 8000
 
-COPY . /armada
-RUN apt-get update && \
+ENTRYPOINT ["./entrypoint.sh"]
+CMD ["server"]
+
+RUN mkdir -p /armada && \
+    apt-get update && \
     apt-get install -y --no-install-recommends \
         netbase \
         curl \
         git && \
     useradd -u 1000 -g users -d /armada armada && \
-    chown -R armada:users /armada && \
-    mv /armada/etc/armada /etc/ && \
-    cd /armada && \
-    python3 setup.py install && \
     rm -rf \
         /root/.cache \
         /var/lib/apt/lists/*
 
-EXPOSE 8000
-
-USER armada
 WORKDIR /armada
 
-ENTRYPOINT ["./entrypoint.sh"]
-CMD ["server"]
+COPY requirements.txt /tmp/
+RUN pip3 install -r /tmp/requirements.txt
+
+COPY . /armada
+
+RUN \
+    mv /armada/etc/armada /etc/ && \
+    cd /armada && \
+    chown -R armada:users /armada && \
+    python3 setup.py install
+
+USER armada