osd: stop scrub_purged_snaps() from ignoring osd_beacon_report_interval

osd: stop scrub_purged_snaps() from ignoring osd_beacon_report_interval

OSD beacons could be burdersome to the enitre cluster, as they lead
to generation of new `OSDMap` epochs. Therefore their frequency is
restricted through `osd_beacon_report_interval` to 5 mins by default.

Unfortunately, the `OSD::send_purged_snaps()` is unaware about this
policy with the net result being storm of OSDMaps. This patch unifies
its behavior with `OSD::tick_without_osd_lock()`.

Fixes: https://tracker.ceph.com/issues/72412
Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>