require a successful write request before concluding pushsync was attempted as a forwarder

On top of the current information, the returned data are
extended by: label, depth, amount, bucketDepth,
blockNumber, and immutableFlag.

This reverts commit e1025971.

Co-authored-by: Anatol Lupacescu <anatollupacescu@gmail.com>
Co-authored-by: Ralph Pichler <pichler.ralph@gmail.com>