Add using share-server backend details in Generic driver

Method setup_network returns server data:
 - instance_id
 - ip
 - authentication data
 (username, password, private key path)

Removed storing server info in memory.
Renamed method get_service_instance to set_up_service_instance.

Removed discover_service_instance method.
Added method ensure_service_instance to check if
instance is running.

Partially-Implements bp implement-backend-details-in-drivers

Change-Id: I857f47510db8d575b3003491b3d3d49a54cf15f5
Merge "Add using share-server backend details in Generic driver"