Repeating the test in e00019.vtc with HTTP/2 fails both here and
for standard Varnish. My understanding of HTTP/2 is too poor for
me to know whether there is a bug in a Varnish, or if I am not
applying HTTP/2 correctly. More details in the comments of the vtc.

Setting this aside for now, but we should come back, but we should
come back to it (and if necessary file a Varnish bug report).