Merge pull request #339 from puppetlabs/pdksync_(MAINT)_Pin_puppetlabs-puppet_agent

pdksync - (CONT-768) Pin puppetlabs-puppet_agent

Author: david22swan

.fixtures.yml

@@ -3,5 +3,7 @@ fixtures:
     reboot: "#{source_dir}"
   repositories:
     facts: 'https://github.com/puppetlabs/puppetlabs-facts.git'
-    puppet_agent: 'https://github.com/puppetlabs/puppetlabs-puppet_agent.git'
+    puppet_agent:
+      repo: 'https://github.com/puppetlabs/puppetlabs-puppet_agent.git'
+      ref: v4.12.1
     provision: 'https://github.com/puppetlabs/provision.git'