The Linux iSCSI initiator toolchain has the dubious feature that
if you ever run the 'sendtargets' command to merely query what
targets are available from a server, the results will be recorded
in /var/lib/iscsi. Any time the '/etc/init.d/iscsi' script runs
in the future, it will then automatically login to all those
targets. /etc/init.d/iscsi is automatically run whenever a NIC
comes online.

So from the moment you ask a server what targets are available,
your client will forever more automatically try to login to all
targets without ever asking if you actually want it todo this.

To stop this stupid behaviour, we need to run

  iscsiadm --portal $PORTAL --target $TARGET
   --op update --name node.startup --value manual

For every target on the server.

* src/storage/storage_backend_iscsi.c: Disable automatic login
  for targets found as a result of a 'sendtargets' command