Follows-up 746d67f5fc which implicitly caused the APCUBagOStuff
object to no longer have a wiki-dependent keyspace. This meant
that all cache keys were shared across wikis, even if they used
makeKey() instead of makeGlobalKey() because the keyspace was
not defined (e.g. it was the string "local" for all wikis, instead
of a string like "enwiki").
Bug: T247562
Change-Id: I469e107a54aae91b8782a4dd9a2f1390ab9df2e5
ae6b99bf65