[gPXE] Only register bios drive without booting

[Andrey Kuzmin]

> The simplest thing to do is
> - to have one HDD in the computer system
> - installed Windows 7 to it
> - make sure networking is fully functional
> - make sure an iSCSI test succeeds to validate your iSCSI target setup
> - remove the HDD and either attach it to your iSCSI target system or
> take a raw HDD image and serve that from the iSCSI target system

No much luck yet. So what I did:

1)  Deleted  all partitions from 160Gb drive and installed win 7 to it
with automatic partitioning
2)  Launched  iscsi  initiator on fresh Win7, this enabled iSCSI service and
I've found LUNs on iscsitarget in initiator
3)  Shutdown,  attached  HDD  to  iscsitarget  server  and setup iscsi
LUN as blockio
4)  Diskless  PC  started  to  boot successfully from iSCSI target, at
least Starting Windows appears
5) After 1-2 minutes windows logo was shown
6)  From  this  time  I  see no any activity in dstat on iscsi target.
Diskless PC waits for 3-4 minutes and reboots.