calamari_rest: filter noncontactable servers from log candidates
calamari_rest: filter noncontactable servers from log candidates

Avoid servers that have no 'last_contact' time, which avoids problems
trying to parse the date to sort them.

Fixes: 7754
Signed-off-by: Dan Mick <b07550071eaa6a9296289c43bbd6c90559196431@inktank.com>

r0h4n/ceph-integration