Adjust style for test-kitchen finstyle

This commit corrects some style issues that clash with the maintainer's
custom style for this project. Some of these included preferring
double-quotes instead of single quotes, removing whitespace, and
general grammar like is_a over kind_of.
 This is something that confused me for a bit too, but the specific rubocop [rules](https://github.com/fnichol/finstyle) for test-kitchen call for double quotes over single quotes.