Handle the pluginsync setting deprecation

In Puppet 4 the pluginsync setting was deprecated. At least in Puppet 5
it generates a deprecation warning and in Puppet 6 it was removed.
Because the default was already true, we only emit it if it's
non-default to avoid the deprecation warning. In Puppet 6 we can detect
an invalid setting so we hard fail.

Author: ekohl

manifests/agent/config.pp

@@ -6,7 +6,6 @@
     'localconfig':       value => '$vardir/localconfig';
     'default_schedules': value => false;
     'report':            value => $::puppet::report;
-    'pluginsync':        value => $::puppet::pluginsync;
     'masterport':        value => $::puppet::port;
     'environment':       value => $::puppet::environment;
     'listen':            value => $::puppet::listen;
@@ -32,6 +31,16 @@
     }
   }
 
+  unless $::puppet::pluginsync {
+    if versioncmp($facts['puppetserver'], '6.0.0') >= 0 {
+      fail('pluginsync is no longer a setting in Puppet 6')
+    } else {
+      puppet::config::agent { 'pluginsync':
+        value => $::puppet::pluginsync,
+      }
+    }
+  }
+
   $::puppet::agent_additional_settings.each |$key,$value| {
     puppet::config::agent { $key: value => $value }
   }