mds: trim cache regularly for standby-replay

mds: trim cache regularly for standby-replay

This change is slightly awkward because standby-replay MDS do not do all
the kinds of upkeep a normal active MDS does. In particular, it is not
going to recall client state from clients.

This diff also merges the extra recall_client_state in
MDCache::check_memory_usage into its only caller (the upkeep thread)
where it was also doing a recall. That's just a matter of merging the
recall flags. This has the added benefit of making
MDCache::check_memory_usage callable for all MDS daemons regardless of
state.

Fixes: https://tracker.ceph.com/issues/50048
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>