Do not re-enable replication when comparing write-behaviour

By default, the value of the setting reset_replication of the Diff router is true.

That will cause the Diff router to try to re-enable the replication from the main to other when the Diff router is stopped after a read-write comparison. In the general case, that will fail so better to not attempt that by default as it will only cause a confusing error message to be logged.