Firstboot fix_partuuid issues

[procount]

The call to fix_partuuid here ->

raspberrypi-sys-mods/usr/lib/raspberrypi-sys-mods/firstboot

Line 227 in 8f1815e

fix_partuuid

is causing problems with NOOBS/PINN.
PINN has already changed the partuuid, so there is no need to adjust it again on first boot as is requried for a raw image.
It means PINN can no longer find the old partuuid (especially related to Edit Config and Replacing an OS with another) because the adjusted partuuid does not match the entry in installed_os.json.

Could you possibly wrap this call within an "If Not 'NOOBS'" condition?

cc: @XECDesign