chore(Dockerfile): consolidate a few chmod and chown into one layer (#54)

Author: helgi

rootfs/Dockerfile

@@ -4,7 +4,7 @@ RUN mkdir /app
 RUN addgroup --quiet --gid 2000 slug && \
     useradd slug --uid=2000 --gid=2000 --home-dir /app --no-create-home \
         --shell /bin/bash
-RUN chown slug:slug /app
+
 WORKDIR /app
 
 # add default port to expose (can be overridden)
@@ -14,10 +14,11 @@ EXPOSE 5000
 ADD ./runner /runner
 ADD ./bin /bin
 ADD https://storage.googleapis.com/object-storage-cli/bb8e054/objstorage-bb8e054-linux-amd64 /bin/objstorage
-RUN chmod +x /bin/objstorage
-RUN chown slug:slug /runner/init
-RUN chown slug:slug /bin/get_object
-RUN chown slug:slug /bin/objstorage
+RUN chmod +x /bin/objstorage && \
+    chown slug:slug /app \
+                    /runner/init \
+                    /bin/get_object \
+                    /bin/objstorage
 
 USER slug
 ENV HOME /app