[S390] dasd: fail requests when device state is less then ready

A DASD device that is not ready or online has no defined disk layout,
so all requests that arrive in such a state need to be returned as
failed.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>