firewall: show zone names in "Add services" dialog
firewall: show zone names in "Add services" dialog

Previously we were showing zone IDs here, which was inconsistent with
what we show in the Zones list on the main firewall page.  Show the
human-friendly name instead.

Fixes #11836
Closes #11842
garrett/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,garrett/cockpit,martinpitt/cockpit,deryni/cockpit,cockpituous/cockpit,deryni/cockpit,deryni/cockpit,cockpituous/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,martinpitt/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,mvollmer/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit