add role_attr_flags parameter to postgresql_user

Pass role_attr_flags a list of comma separated role
attributes when creating or updating a user.

examples/playbooks/postgresql.yml

@@ -36,3 +36,6 @@
 
   - name: ensure user has access to database
     action: postgresql_user db=$dbname user=$dbuser password=$dbpassword priv=ALL
+
+  - name: ensure user does not have unnecessary privilege
+    action: postgresql_user user=$dbuser role_attr_flags=NOSUPERUSER,NOCREATEDB