H2 truncates certain contents on master

This seems to be a regression, since it does not happen on 6.1.x. I haven't dug deeper into it, but in the case I found, ATS closes the stream after 2 data frames (8k + a few bytes), where it really needs to send about 27KB.

I've reverted my server to 6.1.x for now, but I'll see if I can find something to reproduce it on e.g. docs.trafficserver.