(#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.
Merge branch 'pull-513' into stable

This closes GH-513
Merge branch 'stable' into facter-2