Change the order of steps and add another check screen.

Since GDM shows the "system-menu-button", it could not correctly
switch users on a locked screen. I added a check to see
if we are on a locked screen and behave accordingly.

needles/gnome/locked_screen_switch_user-20200422.json

@@ -0,0 +1,15 @@
+{
+  "properties": [],
+  "tags": [
+    "locked_screen_switch_user"
+  ],
+  "area": [
+    {
+      "xpos": 964,
+      "ypos": 709,
+      "width": 21,
+      "height": 19,
+      "type": "match"
+    }
+  ]
+}

tests/desktop_login.pm

@@ -139,7 +139,11 @@ sub logout_user {
 sub switch_user {
     # Switch the user, i.e. leave the current user logged in and
     # log in another user simultaneously.
-    if (check_screen "system_menu_button") {
+    send_key "ret";
+    if (check_screen "locked_screen_switch_user") {
+        assert_and_click "locked_screen_switch_user";
+    }
+    elsif (check_screen "system_menu_button") {
         # The system_menu_button indicates that we are in an active
         # and unlocked session, where user switching differs
         # from a locked but active session.
@@ -150,10 +154,6 @@ sub switch_user {
         # Add sleep to slow down the process a bit
         sleep 10;
     }
-    else {
-        # When the screen is locked, use the icon.
-        assert_and_click "locked_screen_switch_user";
-    }
 }
 
 sub reboot_system {