Re-enable offline upgrades on fixedfunction with AUM
The apertis-update-manager already works on the Fixed Function OSTree images for online updates, but to support offline bundles it needs the udisks2 package to be installed.
This was the case in previous release streams since it was pulled indirectly by Canterbury/Ribchester, but with the minimization of the components in the Fixed Function image it has been dropped.
The downside of this is that offline upgrades could only be tested on the HMI images and that this would rule out testing them on the arm64 R-Car board since we do not build HMI for those due to the lack of any open graphical stack.
By explicitly installing udisks2 on fixedfunction images it will be
possible to test offline upgrades on R-Car again.