Write tests

[ethack]

At the very least ensure that running zeek --version and zeekctl --version don't error. Another test would be to run zeekctl check to make sure no plugin has caused issues. But to do that we'll need to make a node.cfg file. Maybe a static one will work, otherwise use the "auto" feature of zeekcfg and generate one on the fly.

Any failures should prevent the zeek image from being pushed to Dockerhub.