(#22107) Force ASCII-8BIT encoding on raw data in property lists

Ruby-1.9 and up default to UTF-8 encoding for strings, but CFData is
used to store bytestrings in plists as read from file-like objects.  So,
disregard the encoding returned from `obj.read`, treating the string as
a bytestring.

I'll admit that it's more than a little yucky that a puppet provider is depending on a library stashed away in puppet/util.