app/testpmd: fix mempool creation by socket id

app/testpmd: fix mempool creation by socket id

The test assumes the socket ids are contiguous. This
is not necessarily the case on all servers and may cause
mempool creation to fail.

Fixing it by detecting the list of valid socket ids and
use it for the mempool creation.

Fixes: 7acf894d07d1 ("app/testpmd: detect numa socket count")
Cc: stable@dpdk.org
Signed-off-by: Shahaf Shuler <shahafs@mellanox.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>