test: Add stress test to Services page
test: Add stress test to Services page

This reproduces the browser spinning at 100% CPU and making the page
stuck for a long time when a lot of systemd events happen at the same
time in a batch. daemon-reload has a similar, but less dramatic effect.

martinpitt/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpituous/cockpit,garrett/cockpit,cockpituous/cockpit,martinpitt/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,mvollmer/cockpit,garrett/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,garrett/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,cockpituous/cockpit,cockpit-project/cockpit,deryni/cockpit,mvollmer/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,deryni/cockpit,cockpituous/cockpit,cockpit-project/cockpit,deryni/cockpit,mvollmer/cockpit