use size instead of length (will have to change when going to Puppet 3)

manifests/kerberos/krb5_conf.pp

@@ -206,7 +206,7 @@ define base::kerberos::krb5_conf (
     }
     'custom': {
       # Verify that the needed parameters are set.
-      if (length($kdcs) == 0) {
+      if (size($kdcs) == 0) {
         fail("when using a 'custom' environment you must define the kdc's")
       }
       if ($master_kdc == undef) {