Updates to process for adding osd

A few items are addressed in this commit:
* crowbar_wall is not longer used, replaced by the
BarclampLibrary::Barclamp::Inventory::Disk methods
* ceph-disk now handles disks without partitions properly, removed the
kludge which was used in the bobtail version
* Only act on disks without partitions
* If a partition is found print a warning and skip the disk

Signed-Off-By: JuanJose 'JJ' Galvez <juanjose.galvez@inktank.com>