Ensure db and db users created before validation

Ensure that for PostgreSQL backends, the database validation functions
are not run until the initial database creation and user role creation
has been completed.

Closes-Bug: #1298605

manifests/init.pp

@@ -104,7 +104,7 @@ class puppetdb(
       database_name          => $database_name,
       database_username      => $database_username,
       database_password      => $database_password,
-      before                 => Class['puppetdb::server']
+      before                 => [Class['puppetdb::server'],Class['puppetdb::server::validate_db']],
     }
   }
 }