Don't let migration block startup. Hence we will allow local requests during migration.
Only remove the alert if successfully migrate
Paranoid catch / log for some odd uncaught failure in migration, seen in the wild.
Convert NPE to ERROR on calling completedInit() twice
Fix back compatibility of keys: Only fill in the top block data if we have a top size; at the moment we never have a top size, because of a bug. I will add a bug to actually implement top block data.