mon: initialize ProgressEvent::add_to_ceph_s

mon: initialize ProgressEvent::add_to_ceph_s

The add_to_ceph_s field was not initialized causing unit
test failures from check-generated.sh:

**** ProgressEvent test 1 dump_json check failed ****
   ceph-dencoder type ProgressEvent select_test 1 dump_json > /tmp/typ-akwRrjNtt
   ceph-dencoder type ProgressEvent select_test 1 encode decode dump_json > /tmp/typ-iDmGaq17A
4c4
<     "add_to_ceph_s": false
---
>     "add_to_ceph_s": true

Fixes: https://tracker.ceph.com/issues/63950
Signed-off-by: Prashant D <pdhange@redhat.com>