When upgrading FCV from 7.0 to 7.1, there is a phase in which we migrate audit config from the config.settings collection to the cluster parameters collection. When this happens, the in-memory audit config is updated to match the new one. However, since we are still in transitional 7.0-to-7.1 FCV while this happens, the audit synchronize job on mongod can run after this migration and overwrite the in-memory audit config, resulting in an unexpectedly empty timestamp. The fix is to block the audit synchronize job on mongod while we are in this transitional state.