properly signal when we exit on error
properly signal when we exit on error

Signed-off-by: António Meireles <9056f7c1f560fe4e0c75ab3cde8bee0cf3d504f4@reformi.st>

AntonioMeireles/coreos-xhyve,AntonioMeireles/corectl,AntonioMeireles/corectl,AntonioMeireles/coreos-xhyve,TheNewNormal/corectl,TheNewNormal/corectl