Revert "Merge branch 'tickets/master/8011' of git://github.com/domcleal/puppet"

This reverts commit 4557e512e8ab6d021481557ecf3b50b606da2929, reversing
changes made to 25213bfcd0c3bf1b5b59131d91490268b4949374.

The code was relying on calling String#map, which doesn't work in Ruby
1.9. The proper thing would be to ensure that resource[:source] is
always an array at the type level but this would potentially break
other providers.