app/testpmd: fix lack of flow action configuration

app/testpmd: fix lack of flow action configuration

Configuration structure is not optional with flow rule actions that expect
one; this pointer is not supposed to be NULL and PMDs should not have to
verify it.

Like pattern item spec/last/mask fields, it is currently set when at least
one configuration parameter is provided on the command line. This patch
sets it as soon as an action is created instead.

Fixes: 7a91969ad35e ("app/testpmd: add various actions to flow command")
Cc: stable@dpdk.org
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>