Depends on D16115. Ref T11044. In the brave new world of multiple masters, we need to check the schemata on each master when looking for missing storage patches, keys, schema changes, etc.
This realigns all the "check out what's up with that schema" calls to work for multiple hosts, and updates the web UI to include a "Server" column and allow you to browse per-server.
This doesn't update bin/storage, so it breaks things on its own (and unit tests probably won't pass). I'll update that in the next change.