print test seed chain in REPRODUCE string

It would be nice to have the whole seed chain in the reproduce
string. This way one only has to add a test.iters=N behind it to
run the test in a loop.

I assume this is needed because of https://github.com/elasticsearch/elasticsearch/commit/aa3897280c17979f79bfcc29072b40dcca519739
Does that make sense? Or is there any other way to achieve this?