app/testpmd: fix weak RSS hash key for flow

app/testpmd: fix weak RSS hash key for flow

The default RSS hash key automatically provided by testpmd for RSS actions
specified without one is so weak that traffic can't spread properly on L4
with it (as seen with TCPv6).

It is only 30 bytes long, zero-padded to RSS_HASH_KEY_LENGTH (64 bytes),
later truncated to 40 bytes for most PMDs. The presence of padding is
really what kills balancing.

This patch provides a full 64-byte (non-zero-terminated) string to address
this issue.

Fixes: d0ad8648b1c5 ("app/testpmd: fix RSS flow action configuration")
Cc: stable@dpdk.org
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>