Do some cleanup of the netback init and deinit code:
- add an omnipotent queue deinit function usable from
xenvif_disconnect_data() and the error path of xenvif_connect_data()
- only install the irq handlers after initializing all relevant items
(especially the kthreads related to the queue)
- there is no need to use get_task_struct() after creating a kthread
and using put_task_struct() again after having stopped it.
- use kthread_run() instead of kthread_create() to spare the call of
wake_up_process().
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>