services: Display error instead of being stuck on loading page
services: Display error instead of being stuck on loading page

When some of the dbus calls have failed the page would stay stuck on the
loading page. Now it shows error.

mvollmer/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit