orch/cephadm: fix osd.default creation

orch/cephadm: fix osd.default creation

The 'ceph orch daemon add osd' path mishandles osd.default which can
can save an incomplete osd.default spec (wrong store key, incomplete
spec, and apply ordering) and can skip work or reject valid LV paths.

This commit validates before saving, persists the full device
selections, matches the spec store by service name, and forces OSD
creation so each command is actually executed.

Fixes: https://tracker.ceph.com/issues/75670
Signed-off-by: Guillaume Abrioux <gabrioux@ibm.com>