target: Implement mode page 0x1c, "Informational Exceptions"

The Windows SCSI compliance test asks for this mode page, and it's
easy to implement: we can just return all 0s to show we don't support
any of these features.

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>