This patch is originally from Alan Stern (as569).  It has been rediffed
against a current tree.

This patch converts usb-storage to use the kthread API for creating its
control and scanning threads.  The new code doesn't use kthread_stop
because the threads need (or will need in the future) to exit
asynchronously.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NMatthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>