OSD collector does not detect encrypted bluestore devices

[wyllys66]

The code for detecting whether or not an OSD is encrypted does not do any checking if the device is bluestore., it just assumes "encrypted = 0".

One possible fix would be to check the path of the block device, similar to the filestore check:

linkpath = os.readlink(block_link)
encrypted = linkpath.startswith('/dev/mapper')

[pcuzner]

the code pre-dates the the introduction of ceph-volume and lvm based OSDs. Unless I'm mistaken, just checking for the /dev/mapper entry would pick up and OSD defined with LVM too. I think the fact that an osd is encrypted should be part of the osd metadata, which could then be exposed by the prometheus exporter.