It's the thing that owns the secrets anyway, and it simplifies things to
have the secrets handling there instead of half in NMActRequest and
half in NMManager. It also means we can get rid of the ugly signals
that NMSettingsConnection had to emit to get agent's secrets, and
we can consolidate the requests for the persistent secrets that the
NMSettingsConnection owned into NMSettingsConnection itself instead
of also in NMAgentManager.
Since the NMActRequest and the NMVPNConnection classes already tracked
the underlying NMSettingsConnection representing the activation, its
trivial to just have them ask the NMSettingsConnection for secrets
instead of talking to the NMAgentManager. Thus, only the
NMSettingsConnection now has to know about the agent manager, and it
presents a cleaner interface to other objects further up the chain,
instead of having bits of the secrets request splattered around the
activation request, the VPN connection, the NMManager, etc.
When a user makes an explicit request for secrets via GetSecrets
or activates a device, don't ask other users' agents for secrets.
Restrict secrets request to agents owned by the user that made the
initial activate or GetSecrets request.
Automatic activations still request secrets from any available agent.
A client calling GetSecrets on the connection should also request
secrets from agents in that client's session. ie, a connection
editor should be able to call GetSecrets, and get the secrets
stored by the agent in that session (the applet).
Simplifies code internally, and makes it easier for clients as well in
some cases where they want to control what ends up in the resulting
hash and what does not.
