catchup incorrectly checks the timeline history in some cases

In cases where:
1.the original database is no longer on timeline 1
2.the target database does not lag behind the original one in timeline,
sanity checks for incremental catchup give a false alarm and prevent databases from being synchronized with an error
ERROR: Destination is not in source timeline history

Thanks to Vadim Ponomarev ("Скала-Р") for pointing out this error.