pktgen: update functions.sh with add_device and reset_all_threads

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
pktgen: unit_test01 for testing race conditions in pktgen

Test program used while rewriting locking in pktgen, for
provoking race conditions between pktgen_add_device() and
pktgen_remove_device().

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>