adapt ceph status detail to luminous and make it more robust

adapt ceph status detail to luminous and make it more robust

they restructured the json interface
(e.g. they removed the timechecks from ceph status)

so we have to generate those differently

also make the whole thing more robust to changes,
as in do not bail out if one thing is missing, but check the needed
data only when we need it and omit that part

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>