hardware: make get_constraints to return topology for hugepages

Whether a numa node is defined or not, if using hugepages we
should create an numa instance topology.

Work-Item: Enhance libvirt driver to report available
           large pages per NUMA node in the host state data

Partial-Implement: blueprint virt-driver-large-pages
Change-Id: I23e0ca58bd8c6a16bff5d36c5d108056e4135351
Merge "hardware: make get_constraints to return topology for hugepages"