target: Fix compatible reservation handling (CRH=1) with legacy RESERVE/RELEASE

This patch addresses a bug with target_check_scsi2_reservation_conflict()
return checking in target_scsi2_reservation_[reserve,release]() that was
preventing CRH=1 operation from silently succeeding in the two special
cases defined by SPC-3, and not failing with reservation conflict status
when dealing with legacy RESERVE/RELEASE + active SPC-3 PR logic.

Also explictly set cmd->scsi_status = SAM_STAT_RESERVATION_CONFLICT during
the early non reservation holder failure from pr_ops->t10_seq_non_holder()
check in transport_generic_cmd_sequencer() for fabrics that already expect
it to be set.

This bug was originally introduced in mainline commit:

commit eacac00c
Author: Christoph Hellwig <hch@infradead.org>
Date:   Thu Nov 3 17:50:40 2011 -0400

    target: split core_scsi2_emulate_crh

Reported-by: Martin Svec <martin.svec@zoner.cz>
Cc: Martin Svec <martin.svec@zoner.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>