Reduce the amount of data sent to avoid a hang in the QUIC stack when
the fifos get full. This fixes the QUIC tests in debug mode while
https://gerrit.fd.io/r/c/19823/ is not merged.
Change-Id: I1ed4c5dc3d41c09bc674de808f3778a074b15454
Type: test Signed-off-by: Aloys Augustin <aloaugus@cisco.com>