(PUP-3997) Create site.pp with root:root permissions

Previously, the test created a `site.pp` on agent nodes without
specifying the owner and group, so the `create_test_file` method
defaulted the owner and group to `puppet`. However, the `puppet` user
isn't present on agent-only hosts.

This commit modifies the test to specify owner and group as `root`. The
test is confined to not run on Windows agents, so this is not an issue.

acceptance/tests/config/apply_file_metadata_specified_in_config.rb

@@ -10,7 +10,7 @@
 agents.each do |agent|
   logdir = get_test_file_path(agent, 'log')
 
-  create_test_file(agent, 'site.pp', <<-SITE)
+  create_test_file(agent, 'site.pp', <<-SITE, :owner => 'root', :group => 'root')
   node default {
     notify { puppet_run: }
   }