[S390] kernel: Print an error message if kernel NSS cannot be defined

If a named saved system (NSS) cannot be defined or saved, print out an
error message with the return code of the underlying z/VM CP command.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>