scsi: qla2xxx: Delete session for nport id change

This patch fixes regression introduced by commit a4239945 ("scsi:
qla2xxx: Add switch command to simplify fabric discovery") by scheduling
session deletion when Nport ID changes.

[mkp: clarified commit]

Fixes: a4239945 ("scsi: qla2xxx: Add switch command to simplify fabric discovery")
Cc: <stable@vger.kernel.org>
Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>