tests: xmonad less dependent on timings

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