Permit setting of grafana_package prefix without using extra-vars

[kunickiaj]

It's not currently possible to set grafana_package outside of using extra-vars because it's set by role vars.

If I want to install the grafana-enterprise package I currently must override the yum repo template, but then set grafana_package using extra vars. It would make it simpler for users to install the enterprise binaries if there were a flag in the normal vars for this.

If this seems like a reasonable ask, I'm happy to open a PR.

• Role version:

  0.17.0

• Ansible version information:

  ansible 2.8.13

[paulfantom]

Seems good to me, please open a PR.

[SuperQ]

This role has been deprecated in favor of a the grafana-ansible-collection collection.