Originally, it wasn't allowed to specify both a port and a name. It is
now, so update the manpage.
<listitem>
<para>
Specifies the name of the export that we want to use.
- Required if the port is not specified, not allowed in the
- other case.
+ Required if the port is not specified; changes the default
+ port for newstyle negotiation from 10809 in the other case.
</para>
<para>
When this option is specified, nbd-client uses the newstyle