Fixing symlink message calling nonexistent variable

The bug was generating this error:

/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/rspec-puppet-0.1.6/lib/rspec-puppet/setup.rb:113:in `safe_make_symlink': undefined local variable or method `file' for RSpec::Puppet::Setup:Class (NameError)

Fixed by calling the right parameter.