test: Add expected messages for TestConnection.testCockpitDesktop
test: Add expected messages for TestConnection.testCockpitDesktop

polkit sometimes logs "Refusing to render service to dead parents." when
shutting down the synthetic browser test. It doesn't seem to happen in
CI, but on my machine the timing is just right to be > 90% reproducible.

The other two sometimes happen when shutting down the bridge in a bad
moment.

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