Fix executing CNI addons commands (fixes #594)

[deric]

This PR attempts to fix some changes introduced in #592 and #575.

• Wrap commands in single array
• Don't use double quotes for strings where string interpolation isn't needed
• Avoid unnecessary code duplication

The exec containing command in form

['kubectl', 'get', 'nodes']

will print help message to stdout instead of executing kubectl get nodes.

[puppet-community-rangefinder]

kubernetes::kube_addons is a class

that may have no external impact to Forge modules.

This module is declared in 0 of 580 indexed public Puppetfiles.

---

These results were generated with Rangefinder, a tool that helps predict the downstream impact of breaking changes to elements used in Puppet modules. You can run this on the command line to get a full report.

Exact matches are those that we can positively identify via namespace and the declaring modules' metadata. Non-namespaced items, such as Puppet 3.x functions, will always be reported as near matches only.

[chelnak]

This looks great. It goes further than my branch right now because you are addressing test issues too.

I have left a couple of comments that I'd like you to address before we merge.

[chelnak]

Looking good @deric