Fix repo setting logic in global config

fixes QubesOS/qubes-issues#9366
fixes QubesOS/qubes-issues#9868
fixes QubesOS/qubes-issues#8802

Author: marmarta

qubes_config/global_config/updates_handler.py

@@ -200,14 +200,21 @@ def save(self):
         if not self.repos:
             return
         for repo_dict in self.repo_to_widget_mapping:
-            found = False
+            # the logic here goes: we have two kinds of widgets,
+            # radio buttons for dom0 update (where we want to enable everything up to
+            # the selected option)
+            # checkbuttons for everything else (where we just want to enable/disable
+            # based on state)
+            dom0_found = False
             for repo, widget in repo_dict.items():
-                try:
-                    if widget.get_active():
-                        found = True
-                        self._set_repository(repo, True)
+                state = widget.get_active()
+                if "dom0" in repo:
+                    if state:
+                        dom0_found = True
                     else:
-                        self._set_repository(repo, not found)
+                        state = not dom0_found
+                try:
+                    self._set_repository(repo, state)
                 except RuntimeError as ex:
                     raise qubesadmin.exc.QubesException(
                         "Failed to set repository data: " f"{escape(str(ex))}"