app/testpmd: fix copy of raw flow item - revisited

app/testpmd: fix copy of raw flow item - revisited

While previous fix with the same title does address the main issue, root
cause is that proper handling of spec/last/mask was overlooked in the
original patch.

Mask and last fields must be taken into account at all times.

Fixes: d0ad8648b1c5 ("app/testpmd: fix RSS flow action configuration")
Fixes: 67af7ecc52ec ("app/testpmd: fix copy of raw flow item")
Cc: stable@dpdk.org
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>