This partially reverts commit d7608ca192.
This was not actually an improvement over just doing the access as root.
The auth-dialog is not run by NM directly. Instead, it requests secrets
via DBus from anybody who implements the SecretAgent interface. It's
then e.g. nm-applet who starts the auth-dialog. But this can really be
anybody, i.e. it's easy to return arbitrary information to the plugin.
So we can't trust the returned username. This means that we can't
improve the situation for system-wide connections that don't provide
a username from the config.
We keep resetting the cached agent socket that the commit also added.
Tobias Brunner
e6dc515c97