Asynchronous tasks can only be submitted while the IPA is running.
Further more, the shutdown sequence can not be tracked with a simple
running flag. We can also be in the state 'Stopping' where we have not
yet completed all events, but we must not commence anything new.
Refactor the running_ boolean into a stateful enum to track this.
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>