According to IEEE 802.15.4 (§5.1.6.1, §6.4.2), the MAC sequence numbers should
be initialized to random values. This was already the case in
framer-802154.c:create(), but not in csma.c:send_packet(), sometimes causing
false detections of duplicate MAC-layer packets in other devices when a device
was restarted too quickly. This patch decreases the probability of such an
event.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>