osd: propagate base pool application_metadata to tiers

osd: propagate base pool application_metadata to tiers

If there is application metadata on the base pool, it should be mirrored
to any other tiers in the set.  This aligns with the fact that the
'ceph osd pool application ...' commands refuse to operate on a non-base
pool.

This fixes problems with accessing tiers (e.g., cache tiers) when the
cephx cap is written in terms of application metadata.

Fixes: https://tracker.ceph.com/issues/49788
Signed-off-by: Sage Weil <sage@newdream.net>
(cherry picked from commit 8bcb281a7d91e6daa842aed4ffb416d764dc6bf1)