scsi: Revert "target: iscsi: Wait for all commands to finish before freeing a session"

mainline inclusion
from mainline-v5.6-rc3
commit 807b9515
category: bugfix
bugzilla: 186215, https://gitee.com/openeuler/kernel/issues/I4RP97
CVE: NA

--------------------------------

Since commit e9d3009c introduced a regression and since the fix for
that regression was not perfect, revert this commit.

Link: https://marc.info/?l=target-devel&m=158157054906195


Cc: Rahul Kundu <rahul.kundu@chelsio.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Reported-by: Dakshaja Uppalapati <dakshaja@chelsio.com>
Fixes: e9d3009c ("scsi: target: iscsi: Wait for all commands to finish before freeing a session")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>