Too many netboot images

[Henrik Nilsen Omma]

https://iso.qa.stgraber.org/qatracker/build/All currently has 9 entries for netboot, which is an over-representation considering it is just 3 ISOs (i386, amd64 and sparc) and we usually only test it once per milestone. (it adds to the general clutter, which we should try to reduce)

IMO we should reorganise the Netboot by ISO rather than by flavour. So Netboot i386 would be an ISO and its test cases would be:

 * Edbuntu netboot install
 * Kubuntu netboot install
 * Ubuntu netboot install
 * Xubuntu netboot install

The question then remains where to display these ISOs, since they no longer fit under 'Ubuntu' etc. 'All' seem to be the right answer.

[Stéphane Graber (stgraber)]

The tabs are now auto-generated from the product list.

So renaming the Netboot ISOs to :
Netboot i386
Netboot amd64
Netboot sparc

Will automatically create a new Netboot tab

[DB change : Mark all current Netboot product as disabled (archive only) + Add the 3 new ones]