mgr/devicehealth: fix telemetry stops sending device reports after 48 hours

mgr/devicehealth: fix telemetry stops sending device reports after 48 hours

Telemetry module fetches device metrics which were scraped in the last
"telemetry interval"*2 (=48 hours by default) by calling
_get_device_metrics() with min_sample. _get_device_metrics() fetches the
metrics from omap and breaks on the first one that is older than
min_sample. But because it fetched in ascending order (from oldest to
newest) it was breaking on the first one it received, if it was older
than the interval above. We need to pass min_sample to get_omap_vals()
so it will start fetching from that value.

Fixes: https://tracker.ceph.com/issues/43837
Signed-off-by: Yaarit Hatuka <yaarit@redhat.com>