Slips leaves 1 process in memory after shutting down

To Reproduce:
./slips.py -e 1 -f dataset/test6-malicious.suricata.json -D -o testing_new_version
and then after 3 s
./slips.py -e 1 -f dataset/test6-malicious.suricata.json -S             

ps aux | grep slips shows 1 process, with a PID that's not present in redis-cli hgetall PIDs
