labs: exit after unhandled option
labs: exit after unhandled option

If the user supplies an unhandled option, the script should stop.
With this patch, it does.

Change-Id: If7b490cf8e4f11dcead16b8dee6e6fa6e4aa2f59

openstack/training-labs,dguitarbite/OpenStack-Labs,openstack/training-labs,openstack/training-labs,dguitarbite/OpenStack-Labs,dguitarbite/OpenStack-Labs