dns: return error reason from nm_dns_plugin_update()
For logging, if the plugin fails with update, it should return a reason that we can log. Note that both dnsmasq and system-resolved plugins do the update asynchronously (of course). Hence, usually they never fail right away, and there isn't really possibility to handle the failure later. Still, we should print something sensible for that we need information what went wrong.
Showing with 33 additions and 12 deletions