Cache loader access un-owned variable causing use-after-free memory access error.
These are the two different places that implement this wrong pattern:

• ShardServerCatalogCacheLoader::getDatabase
• CatalogCache::getDatabase

StringData object wraps a 'const std::string&' or a 'const char*' without copying its contents. Thus keeping alive the StringData object itself doesn't guarantee that the underlying char array won't be freed. For this reason when capturing such an object in an async task an explicit copy of the underlying data needs to be performed.