Provide a way to set env vars for selfmedicate.sh

[olberger]

This aims at solving #44

Setting env var value for selfmedicate in the YAML config file so it can
be passed to the provisionner

First variable will be PRELOADED_IMAGES

I'm not completely sure this is the best way to do...

Another variable could be the k8s version in KUBERNETES_VERSION (edited).

Closes #44

[olberger]

Added another variable for the k8version

[olberger]

Btw, this would help address #56

[smk4664]

This didn't work for me, but I am testing another option. Same principle, just loading the variables differently.

Update, this did work, I just didn't fix the self-medicate script to use the variable.

[Mierdin]

To be honest, I'm not quite sure what this change is meant to solve. We're already reading in the antidote config file at the beginning of selfmedicate, so why don't we just delegate all of these options to that script?

[Mierdin]

I'm not quite sure of the purpose of this. Since K8SVERSION should have a default value, let's just install whatever version is indicated there.

To be clear, I am in favor of installing the version under K8SVERSION, so I like the inner change, just not sure of the outer conditional.

[olberger]

I think I aimed at being able to use the provisionning scripts outside the context of Vagrant, thus not necessarily having K8SVERSION set

[Mierdin]

I'm not sure it's clear from this comment when I should modify these values. I think the idea is that if you're both a) using Vagrant and b) wish to override the default values in selfmedicate.sh, you should uncomment this - but I'd like to see more clarity here if that's true. My over-arching comment about why this only applies to Vagrant still stands though.