Move the task cleanup from the task fail callback to taskq_cleanup.
This makes the one failure callback a lot simpler.

Try to schedule a new task for the connection in conn_task_cleanup()
this removes the session_schedule() in the task_pdu_cb().

Rename task_cleanup() to conn_task_cleanup() seems a better place for
this function since it does connections scheduling.

Start implementing the FSM. Introduce a session FSM that is run via a
callback and implement some of the connection FSM actions. Implement
logouts so that discovery sessions do a nice login -> query -> logout.
Fix the task scheduling especially for immediate and connection specific
tasks. The session will now only schedule tasks to a session that is
in LOGGED_IN state.
looks good dlg@

Ugly hack, call session_schedule in the task pdu callback handler.
Without this accessing both LU on my iscsi target will lock up
because tasks a queued but no longer scheduled.
We need a better task scheduler but this allows me to run iogen on both
partitions without locking up.

Implememnt NOP-IN -> NOP-OUT handling. If the NOP-In was issued by the
target (itt = 0xffffffff) send back an immediate NOP-Out reusing the
NOP-In PDU. This makes my iscsi target happy.
Also plug a mem leak on error path which was found by Igor Zinovik.

Log the PDU which failed because no task was found.
Should help identify the messages that are issued by the target (e.g. NOP).

spacing, no binary changes.

fix typos in documentation and log_debug() function.

ok claudio@

iSCSI Initiatior daemon using vscsi(4).
Currently implements the absolute minimum of the protocol to make
it work against targets. Many things still in flux but we're annoyed
to work outside of the tree. Commited from a source tree on an iSCSI
disk served via iscsid but it is not yet production ready.
OK dlg@, matthew@, deraadt@