improvement(docker): smaller images via no-cache option (via #5157)

* add no-cache option for smaller images

* move flag immediately after `apk`

adjusting to be as close to the example as possible: https://github.com/gliderlabs/docker-alpine/blob/master/docs/usage.md#disabling-cache

Dockerfile

@@ -4,7 +4,7 @@
 
 FROM nginx:1.15-alpine
 
-RUN apk add nodejs
+RUN apk --no-cache add nodejs
 
 LABEL maintainer="fehguy"