scsi: iscsi: Drop session lock in iscsi_session_chkready()

scsi: iscsi: Drop session lock in iscsi_session_chkready()

The session lock in iscsi_session_chkready() is not needed because when we
transition from logged into to another state we will block and/or remove
the devices under the session, so no new I/O will be sent to the drivers
after the block/remove. I/O that races with the block/removal is cleaned up
by the drivers when it handles all outstanding I/O, so this just added an
extra lock in the main I/O path. This patch removes the lock like other
transport classes.

Link: https://lore.kernel.org/r/20210207044608.27585-10-michael.christie@oracle.com
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>