Simple unit test that created pcapng file using API.
To run this test you need to have at least one device.
For example:
DPDK_TEST=pcapng_autotest ./build/app/test/dpdk-test -l 0-15 \
--no-huge -m 2048 --vdev=net_tap,iface=dummy
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>