Plugin manager should update app level status (#212)

Currently, whenever the plugin manager is executed, there is an update
of the status in both app and unit level. This PR changes the behavior,
and only the app level should be updated from now on.

lib/charms/opensearch/v0/opensearch_base_charm.py

@@ -492,7 +492,7 @@ def _on_update_status(self, event: UpdateStatusEvent):
         # handle when/if certificates are expired
         self._check_certs_expiration(event)
 
-    def _on_config_changed(self, event: ConfigChangedEvent):
+    def _on_config_changed(self, event: ConfigChangedEvent):  # noqa C901
         """On config changed event. Useful for IP changes or for user provided config changes."""
         if self.opensearch_config.update_host_if_needed():
             self.status.set(MaintenanceStatus(TLSNewCertsRequested))
@@ -521,23 +521,26 @@ def _on_config_changed(self, event: ConfigChangedEvent):
         try:
             if not self.plugin_manager.check_plugin_manager_ready():
                 raise OpenSearchNotFullyReadyError()
-            self.status.set(MaintenanceStatus(PluginConfigCheck))
+            if self.unit.is_leader():
+                self.status.set(MaintenanceStatus(PluginConfigCheck), app=True)
             if self.plugin_manager.run():
                 self.on[self.service_manager.name].acquire_lock.emit(
                     callback_override="_restart_opensearch"
                 )
-            self.status.clear(PluginConfigCheck)
         except (OpenSearchNotFullyReadyError, OpenSearchPluginError) as e:
             if isinstance(e, OpenSearchNotFullyReadyError):
                 logger.warning("Plugin management: cluster not ready yet at config changed")
             else:
-                self.status.set(BlockedStatus(PluginConfigChangeError))
+                self.status.set(BlockedStatus(PluginConfigChangeError), app=True)
             event.defer()
             # Decided to defer the event. We can clean up the status and reset it once the
             # config-changed is called again.
-            self.status.clear(PluginConfigCheck)
+            if self.unit.is_leader():
+                self.status.clear(PluginConfigCheck, app=True)
             return
-        self.status.clear(PluginConfigChangeError)
+        if self.unit.is_leader():
+            self.status.clear(PluginConfigCheck, app=True)
+            self.status.clear(PluginConfigChangeError, app=True)
 
     def _on_set_password_action(self, event: ActionEvent):
         """Set new admin password from user input or generate if not passed."""