fix #1895: use json for 'rbd ls -l' and 'rbd info'

fix #1895: use json for 'rbd ls -l' and 'rbd info'

since ceph changed the plain output format for 12.2.8
we have to change the code anyway, and when were at it,
we can change it to the (hopefully) more robust json output

Co-authored-by: Alwin Antreich <a.antreich@proxmox.com>
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>