Use eap_check_settings directly from network.c before we start the
connection attempt at netdev.c level, to obtain all of the required
passwords/passphrases through the agent. This is in network.c because
here we can decide the policies for whether to call the agent in
autoconnect or only if we had a request from the user, also whether we
want to save any of that for later re-use (either password data or
kernel-side key serial), etc.
In this patch we save the credentials for the lifetime of the network
object in memory, and we skip the network if it requires any passphrases
we don't have while in autoconnect, same as with PSK networks where the
PSK isn't given in the settings. Note that NetworkManager does pop up
the password window for PSK or EAP passwords even in autoconnect.
If EAP needs multiple passwords we will call the agent sequentially for
each.