Do not return error when handling acyclic GCI services unless no ressources are available

The current implemented GCI acyclic service handler uses different return values for various issues. This needs to be changed.

The GCI adapter shall only answer negative to acyclic service request in case he has no ressource to handle the request right now. In that case the GCI application will try again to issue the service at a later point in time.

Other errors, e.g. the same service is already running, need to be handled differently. The acyclic service request needs to be accepted and answered positively. Afterwards a confirmation for the service needs to be prepared and provided to GCI application via ServiceAvailable callback. This service confirmation can have the dedicated status set (e.g. request running).

This prevents endless loops of GCI application and adapter playing ping pong with each other.