[SCSI] iscsi class: remove host no argument from session creation callout

We do not need to have llds set the host no for the session's
parent, because we know the session's parent is going to be
the host. This removes it from the session creation callback
and converts the drivers.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>