OSDMap: reset osd_primary_affinity shared_ptr when deepish_copy_from

OSDMap: reset osd_primary_affinity shared_ptr when deepish_copy_from

Base on current logic, OSDMonitor may call create_pending and
encode_pending twice for the some epoch.

In encode_pending:

tmp.deepish_copy_from(osdmap);
tmp.apply_incremental(pending_inc);

This Op would change the tmp osd_primary_affinity, but the osd_primary_affinity
is declared as ceph::shared_ptr, so this would change the osdmap too. When this
round encode_pending is proposed fail. We may call encode_pending again, but the
osdmap is changed last round, so the pending_inc would be wrong.

Fixes: #14686
Signed-off-by: Xinze Chi <xinze@xsky.com>