fix: disable Dockerfile always check for package updates

[csmart]

set a static datestamp so that apt-get/dnf aren't run each time a new docker container is built. Increment it if you want to refresh the package databases in order to install new software or if something is out of date.

@shenki

---

This change is

[shenki]

Why have the datestamps at all? I think we should remove them._

Also, should be doing the apt-get update && apt-get install as the one run command. See https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/

[csmart]

@shenki yep, pushed new commit.

[shenki]

Looking good! A few more comments.