Add ability to install Snaps with classic confinement

[ikogan]

No description provided.

[javierbertoli]

@ikogan any chance you try to fix the the faliling tests?

A quick peek shows some errors which will problably require something like this

[ikogan]

First, I don't think the errors are reflecting this but the snap used in the example didn't actually exist. That's fixed now.

In terms of the errors, they're happening on master as well and are fairly deep within salt dependencies. I tried for a good while but it looks like there may even be some upstream issues related to this.

Attempting to upgrade Salt creates a different issue, attempting to upgrade pip creates yet another. I'm not quite well versed enough in the Kitchen environment to be able to track this down without a lot more effort than I currently have time for unfortunately.

[javierbertoli]

@ikogan I agree with you. Failures seem to be a totally different issue. I merged this PR and will try to fix tests in another PR.

I appreciate your efforts to try to fix the tests.

[ikogan]

Thanks! Sorry I wasn't able to get them fixed, I look forward to seeing what does fix them so I can learn a bit more about this.