scsi: target: core: Fix preempt and abort for allreg res

Match a key only if SARK is not zero according to SPC-4 and the comment
above the code:

 If an all registrants persistent reservation is present and the SERVICE
 ACTION RESERVATION KEY field is set to zero, then all registrations
 shall be removed except for that of the I_T nexus that is being used
 for the PERSISTENT RESERVE OUT command;

Without this patch in case of SARK==0 no registrants will be removed.

Link: https://lore.kernel.org/r/20220909090425.14479-2-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>