Re: [PATCH 02/10] vpn-provider: React to different error types in connect_cb()

The connection callback (connect_cb()) can be called via vpn-agent.c to indicate that VPN agent dialog had an error or was cancelled in addition to calling the function via VPN plugin. Because of this the different error types should be handled properly. Errors: - EACCES is an authentication error: VPN_PROVIDER_ERROR_AUTH_FAILED. - ENOMSG and ETIMEDOUT are system reported errors and then the agent request needs to be canceled and error set unknown error. - ECANCELED is reported when user canceled VPN agent dialog, treat this as same as ECONNABORTED as the VPN may have been initialized already. - ECONNABORTED is set when connect_cb() is called via VPN plugin. To ensure that proper disconnect -> idle cycle is done both driver and provider are set to disconnect state and eventually killed and put to idle state if the provider was 1) being connected or 2) already connected. - In other cases the VPN provider is set to failure state and connect error is indicated.