Segfault When SMP is Specified

[larkwiot]

To reproduce:

docker pull pandare/panda:latest
docker run --rm -it pandare/panda:latest panda-system-x86_64 -smp 2

[AndrewFasano]

SMP is unsupported in panda. We should have an error message about this instead of segfaulting though.

Related to #152