labs: stop advertizing export option
labs: stop advertizing export option

Exported VMs are currently not very useful. Export/import needs work
at least for network configuration to survive the transport.

Upcoming patches would become more complicated just to preserve the
current export functionality that nobody's using.

This patch does not remove export, but keeps osbash.sh from telling
anyone about its existence.

Change-Id: I4f09fe15b199545e0e7fbc5fa9b3b030a539b934
harrisonfeng/training-guides,openstack/training-guides,harrisonfeng/training-guides,openstack/training-guides,Nabs007/training-guides,Nabs007/training-guides,harrisonfeng/training-guides,Nabs007/training-guides