Fixed an error showed by puppet if the EMPTY file is very large

Got this error in the debian6 machine after running 'vagrant up':
Error: /Stage[main]//File[/EMPTY]: Could not evaluate: Puppet::Util::Log requires a message

When the EMPTY file is very large, puppet uses a lot of memory deleting the file, and if the file is too large it crashes.

The size of the EMPTY file in the debian6 box:
$ du -sh /EMPTY
7.8G    /EMPTY

Added the backup=>false option.