mon/PGMap: fix incorrect pg_pool_sum when delete pool

mon/PGMap: fix incorrect pg_pool_sum when delete pool

We found the pools num diplayed by "ceph -s" is not the same with
"ceph osd lspools" after deleting a pool sometime. The result is
Mgr ClusterState::ingest_pgstats get the old pg_stat which pg is
not deleted in some osd before the pool deleted and add to
pending_inc.pool_statfs_updates. The deleted pool will be added to
pg_pool_sum unconsciously by PGMap::apply_incremental and which has
been deleted in OSDMap. This will also casue MON's Segmentation
fault.

Fixes: https://tracker.ceph.com/issues/42689
Fixes: https://tracker.ceph.com/issues/42592
Fixes: https://tracker.ceph.com/issues/41228
Fixes: https://tracker.ceph.com/issues/40011
Signed-off-by: luo rixin <luorixin@huawei.com>
(cherry picked from commit 446eca8defddda44fea7c789065afdb1a9d38dae)