Add visual dividers for each image in Dockerfile

Our dockerfiles describe the building of many images. Some are temporary
and others persist to publishing, but they all have specific roles and
knowing where to apply changes is important. Unfortanately, it is hard
to see that by default. Experiment with the addition of ==== barrier
lines to give people a visual cue for the divisions.

Change-Id: If28e0bd94a4d65f0623c56e9a589615dd04d2e75

Dockerfile

@@ -14,12 +14,14 @@
 # limitations under the License.
 
 FROM docker.io/opendevorg/python-builder as builder
+# ============================================================================
 
 ARG ZUUL_SIBLINGS=""
 COPY . /tmp/src
 RUN assemble
 
 FROM docker.io/opendevorg/python-base as nodepool-base
+# ============================================================================
 
 COPY --from=builder /output/ /output
 RUN /output/install-from-bindep
@@ -41,16 +43,22 @@ COPY tools/uid_entrypoint.sh /uid_entrypoint
 ENTRYPOINT ["/uid_entrypoint"]
 
 FROM nodepool-base as nodepool
+# ============================================================================
+
 USER 10001
 CMD ["/usr/local/bin/nodepool"]
 
 FROM nodepool-base as nodepool-launcher
+# ============================================================================
+
 USER 10001
 CMD _DAEMON_FLAG=${DEBUG:+-d} && \
     _DAEMON_FLAG=${_DAEMON_FLAG:--f} && \
     /usr/local/bin/nodepool-launcher ${_DAEMON_FLAG}
 
 FROM nodepool-base as nodepool-builder
+# ============================================================================
+
 # dib needs sudo
 RUN echo "nodepool ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/nodepool-sudo \
   && chmod 0440 /etc/sudoers.d/nodepool-sudo