Otherwise the included tasks won't be applied when using tags,
see https://github.com/ansible/ansible/issues/30882#issuecomment-479214591

Closes: #409

Helm 2.15.0 broke for us (#338), and helm 2.15.1 might be responsible
for #357.
We need to upgrade a few components but for the upcoming OAS 0.2.1 release
we stay with helm 2.14.3.

This reverts commit ae877752, reversing
changes made to cd1ad365.

add forgotten helmfile config, add `--validate=false` to kubernetes manifests (https://github.com/jetstack/cert-manager/issues/2208)

Now that helm is working again for our usecase (see details in
https://open.greenhost.net/openappstack/openappstack/issues/339)
we can install helm as snap again.

Closes: #339

This reverts commit 52910021.

We got an `Error: unsupported format` with an auto-updated Helm `2.15.0`
installed from snap.
Now we pin it to a specific working version and use the official install script.

Closes: #295