Reworked some Dockerfiles to improve cache usage.

cmd/controller/Dockerfile

 FROM alpine:3.7
 
-COPY ./bin/controller /home/agones/controller
-COPY ./certs /home/agones/certs
 RUN apk --update add ca-certificates && \
-                adduser -D agones && \
-                chown -R agones /home/agones && \
-                chmod o+x /home/agones/controller
+    adduser -D agones
+
+COPY ./certs /home/agones/certs
+COPY ./bin/controller /home/agones/controller
+
+RUN chown -R agones /home/agones && \
+    chmod o+x /home/agones/controller
 
 USER agones
 ENTRYPOINT ["/home/agones/controller"]
\ No newline at end of file

cmd/sdk-server/Dockerfile

 FROM alpine:3.7
 
-COPY ./bin/sdk-server.linux.amd64 /home/agones/sdk-server
 RUN apk --update add ca-certificates && \
-                adduser -D agones && \
-                chown -R agones /home/agones && \
-                chmod o+x /home/agones/sdk-server
+    adduser -D agones
+
+COPY ./bin/sdk-server.linux.amd64 /home/agones/sdk-server
+
+RUN chown -R agones /home/agones && \
+    chmod o+x /home/agones/sdk-server
 
 USER agones
 ENTRYPOINT ["/home/agones/sdk-server"]
\ No newline at end of file

examples/simple-udp/server/Dockerfile

@@ -14,9 +14,11 @@
 
 FROM alpine:3.7
 
+RUN adduser -D server    
+
 COPY ./bin/server /home/server/server
-RUN adduser -D server && \
-    chown -R server /home/server && \
+    
+RUN chown -R server /home/server && \
     chmod o+x /home/server/server
 
 USER server