iSCSI: statSN during login

["Ayman Ghanem" <aghanem@cisco.com>]

Julian,

There is inconsistency on the use of statSN during login between sections
1.2.2.2:

        Status numbering starts after Login. During login, there is always
        only one outstanding command per connection and status numbering is
        not strictly needed but may be used as a sanity check.

and section 2.13.4:

        For the first Login Response (the response to a Login Request with
        C=0) this is the starting status Sequence Number for the connection
        (the next response of any kind will carry this number + 1). This
        field is valid only if the Status Class is 0.

The later indicates that statSN MUST be used during login phase. Since this
is not really needed during login, I suggest changing the text so that
statSN not to be used until the connection is in full feature phase (similar
to cmdSN).

-Ayman