tests: xmonad less dependent on timings

+1
+1
nixos/tests/xmonad.nix
··· 19 19 $machine->waitForX; 20 20 $machine->waitForFile("/home/alice/.Xauthority"); 21 21 $machine->succeed("xauth merge ~alice/.Xauthority"); 22 + $machine->waitUntilSucceeds("xmonad --restart"); 22 23 $machine->sleep(3); 23 24 $machine->sendKeys("alt-shift-ret"); 24 25 $machine->waitForWindow(qr/machine.*alice/);