Update DNS plug-in on network change

Restart the DNS plug-in on network change. This makes sure any
potential host OS DNS configuration changes get picked up by the DNS
plug-in as well.

supervisor/host/network.py

@@ -282,6 +282,11 @@ async def apply_changes(
                     state = msg[0]
                     _LOGGER.debug("Active connection state changed to %s", state)
 
+                # This potentially updated the DNS configuration. Make sure the DNS plug-in
+                # picks up the latest settings.
+                if not update_only:
+                    await self.sys_plugins.dns.restart()
+
         # update_only means not done by user so don't force a check afterwards
         await self.update(force_connectivity_check=not update_only)