ceph-volume: support mode-specific availability fields in inventory subcommand
There are two modes of OSD, the traditional "lvm mode" and the new "raw mode".
Although LVM mode can only be created on top of raw disk or its partition,
there is no such limitation in raw mode. However, the "available" field
of `ceph-volume inventory` doesn't consider raw mode at all. For example,
crypt type device is regarded as unavailable even though `ceph-volume raw prepare`
can create an OSD in this device. We should support mode-specific availability
fields in `inventory` subcommand.