of `args` itself and as an element inside of an `args` array. Added validation
around passing in arrays for arguments. Just knowing that it is an array is not
enough, because arrays can contain any other type.
The logic change in 57d4775140 introduced
a bug where neither strings nor arrays provided as `args` for shell
provisioners would pass validation.
This fixes that problem along with a few extras:
- split out arg validation into a private method
- update comment describing valid args
- add a few unit tests around config validation
Ryan Uber
Paul Hinze