Binding information for a SchedulerExtensionService.
The attempt ID will be set if the service is started within a YARN application master;
there is then a different attempt ID for every time that AM is restarted.
When the service binding is instantiated in client mode, there's no attempt ID, as it lacks
current spark context
YARN application ID
YARN attemptID. This will always be unset in client mode, and always set in