ceph-osd: Fix start_osds.yml in check mode

This construct doesn't work as intended since ansible/ansible#74212:

```
ceph_osd_ids.stdout | default('{}') | from_json
```

That PR made the `command` module return `stdout` even in check mode (setting
it to the empty string), so `default()` has no effect in that case and
`from_json()` fails to parse an empty string.

Instead, `default()` needs to be invoked with its second argument set to
`True`, so that it replaces any `False` value (such as an empty string) with
its first argument:

```
ceph_osd_ids.stdout | default('{}', True) | from_json
```

Signed-off-by: Benoît Knecht <bknecht@protonmail.ch>
(cherry picked from commit 0b3a608)

Author: BenoitKnecht

roles/ceph-osd/tasks/start_osds.yml

@@ -57,7 +57,7 @@
     mode: "{{ ceph_directories_mode }}"
     owner: "{{ ceph_uid if containerized_deployment | bool else 'ceph' }}"
     group: "{{ ceph_uid if containerized_deployment | bool else 'ceph' }}"
-  with_items: "{{ ((ceph_osd_ids.stdout | default('{}') | from_json).keys() | list) | union(osd_ids_non_container.stdout_lines | default([])) }}"
+  with_items: "{{ ((ceph_osd_ids.stdout | default('{}', True) | from_json).keys() | list) | union(osd_ids_non_container.stdout_lines | default([])) }}"
 
 - name: systemd start osd
   systemd:
@@ -66,4 +66,4 @@
     enabled: yes
     masked: no
     daemon_reload: yes
-  with_items: "{{ ((ceph_osd_ids.stdout | default('{}') | from_json).keys() | list) | union(osd_ids_non_container.stdout_lines | default([])) }}"
+  with_items: "{{ ((ceph_osd_ids.stdout | default('{}', True) | from_json).keys() | list) | union(osd_ids_non_container.stdout_lines | default([])) }}"