Additional bugfix to Kreidl's patch. Solves wipefs issue when trying to preserve.
Ensures that the VG active, before trying to wipe any LV
Fixes preservation issue when attempting a combination of RAID and LVM

Issue was caused by the fact that setup-storage tries to call
vgchange -a n after deactivating the RAID. Added a global array that
keeps a list of RAID devices with "preserve" flags, using the array
FAI::build_lvm_commands then checks if any VG is on a RAID that needs
to be preserved and ensures that vgchange is called (or not called)
accordingly.
make beta