In some obscure scenarios e.g. passing a 0-byte backing file
storage, wait_for_completion() would wait forever in fsg_cleanup().

Prevent it by completing the thread in fsg_bind() error path.
Signed-off-by: NFelipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>