Fixing TaskControllerImpl cancellation issues:
 * moving FLAG_CANCEL_REQ in forceCancel() to separate line to be properly persisted
 * removing FLAG_CANCEL_REQ check from execCancelled() - the flag is never set when Executable.cancelled() is called
renaming test case because new TERMINATE_WAIT task controller state have been introduced
enhancing transitions test case
include finished or cancelled tasks in transition decision too