scsi: iscsi: Report connection state in sysfs

scsi: iscsi: Report connection state in sysfs

If an iSCSI connection happens to fail while the daemon isn't running (due
to a crash or for another reason), the kernel failure report is not
received.  When the daemon restarts, there is insufficient kernel state in
sysfs for it to know that this happened.  open-iscsi tries to reopen every
connection, but on different initiators, we'd like to know which
connections have failed.

There is session->state, but that has a different lifetime than an iSCSI
connection, so it doesn't directly reflect the connection state.

[mkp: typos]

Link: https://lore.kernel.org/r/20200317233422.532961-1-krisman@collabora.com
Cc: Khazhismel Kumykov <khazhy@google.com>
Suggested-by: Junho Ryu <jayr@google.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>