mgr/cephadm: Don't skip OSDs with non-empty osdspec_affinity

mgr/cephadm: Don't skip OSDs with non-empty osdspec_affinity

`ceph cephadm osd activate` calls `deploy_osd_daemons_for_existing_osds`
with a synthetic DriveGroupSpec where service_id=''. Commit fbe3a053
introduced an unconditional osdspec_affinity filter:

    if osd['tags']['ceph.osdspec_affinity'] != spec.service_id:
        continue

The fix is to only enforce the affinity check when spec.service_id is
non-empty. An empty service_id means the caller is osd activate, which
should adopt any existing OSD regardless of its affinity tag.

Fixes: https://tracker.ceph.com/issues/76979
Signed-off-by: Redouane Kachach <rkachach@ibm.com>