Fixes command

Correct command is `test -e $filename`

Also % replacement in validate_cmd is not supported in a released version of puppetlabs-stdlib, it's fixed in 4.5.x but not not released yet (See: puppetlabs/puppetlabs-stdlib#377)

Author: petems

spec/unit/defines/concat_spec.rb

@@ -391,7 +391,7 @@
     end
 
     context '/usr/bin/test -e' do
-      it_behaves_like 'concat', '/etc/foo.bar', { :validate_cmd => '/usr/bin/test % -e' }
+      it_behaves_like 'concat', '/etc/foo.bar', { :validate_cmd => '/usr/bin/test -e' }
     end
 
     [ 1234, true ].each do |cmd|