Improve puppet configuration for EGI StAR accounting

src/puppet/dmlite/manifests/accounting.pp

@@ -50,11 +50,12 @@ class dmlite::accounting (
     }
   }
   # apel-ssm also available in UMD repository
-  if $ssm_url == '' {
+  if $enabled and $ssm_url == '' {
     if $facts['os']['family'] == 'RedHat' {
       $ssm_package_url = $facts['os']['release']['major'] ? {
         '6' => 'https://github.com/apel/ssm/releases/download/2.3.0-2/apel-ssm-2.3.0-2.el6.noarch.rpm',
         '7' => 'https://github.com/apel/ssm/releases/download/2.3.0-2/apel-ssm-2.3.0-2.el7.noarch.rpm',
+        default => fail("EGI StaR accounting enabled but ${facts['os']['name']}${facts['os']['release']['major']} is not supported")
       }
     }
   } else {