firewall: List firewall services alphabetically
firewall: List firewall services alphabetically

When firewall services are list, the order changes for every run of
plinth and is not predictable making it hard to lookup a service.  List
services alphabetically to fix the problem.

vignanl/Plinth,vignanl/Plinth,harry-7/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,harry-7/Plinth,kkampardi/Plinth,vignanl/Plinth,kkampardi/Plinth,harry-7/Plinth,freedomboxtwh/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,vignanl/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,harry-7/Plinth,harry-7/Plinth,vignanl/Plinth,freedomboxtwh/Plinth