scsi: target: core: Fix memory leak in preempt_and_abort

Always release preempt_and_abort_list to avoid memory leak of
t10_pr_registration objects in it.

Link: https://lore.kernel.org/r/20220909090425.14479-3-d.bogdanov@yadro.com


Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>