SCRIPT eval (when failing due to NOSCRIPT) can retry when using the sync API, since there can be no competing commands (but not via the async API)

need to explicitly include an empty net45 section to indicate no deps, otherwise it assumes net40 deps still apply

Fix RedisServer.Save(SaveType.BackgroundSave)

BGSAVE returns "Background saving started" upon success,
RedisServer.Save expected "OK".