Enable EC2 InstanceInitiatedShutdownBehavior of terminate

The EC2 API supports an instance attribute called
InstanceInitiatedShutdownBehavior (IISB) which can be set to
'stop' or 'terminate' (default: 'stop').  When the instance
initiates its own shutdown, this determines whether or not
the instance hangs around in the Shutoff state or is
terminated by the system.

In nova, this is handled by the shutdown_terminate boolean.
IISB = stop      => shutdown_terminate = False
IISB = terminate => shutdown_terminate = True

sync_power_state now invokes terminate_instance if
shutdown_terminate = True and we detect the image power state
has gone from Running to Shutdown.

Fixes bug #1131395

Change-Id: I284ae7a84384f19131703c4ad44e0e5f5b03f5d4
iisb 3

Change-Id: I36908884e7780f99c0f91a6a761c738d4c7b8633