scsi: iscsi: Fail session and connection on transport registration failure

If the transport cannot be registered, the session/connection creation
needs to be failed early to let the initiator know.  Otherwise, the system
will have an outstanding connection that cannot be used nor removed by
open-iscsi. The result is similar to the error below, triggered by
injecting a failure in the transport's registration path.

openiscsi reports success:

root@debian-vm:~#  iscsiadm -m node -T iqn:lun1 -p 127.0.0.1 -l
Logging in to [iface: default, target: iqn:lun1, portal: 127.0.0.1,3260]
Login to [iface: default, target: iqn:lun1, portal:127.0.0.1,3260] successful.

But cannot remove the session afterwards, since the kernel is in an
inconsistent state.

root@debian-vm:~#  iscsiadm -m node -T iqn:lun1 -p 127.0.0.1 -u
iscsiadm: No matching sessions found

Link: https://lore.kernel.org/r/20200106185817.640331-4-krisman@collabora.com
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>