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
virt: pass instance object to block_stats & get_instance_disk_info

The block_stats and get_instance_disk_info methods are the last
two virt driver methods which do not take a full Nova Instance
object. They are trivially convertable.

Blueprint: libvirt-driver-class-refactor
Change-Id: I87ef651383c9b4ab3abe4bf8a5c49501e353abc4
Merge "hardware: make get_constraints to return topology for hugepages"
Merge "virt: pass instance object to block_stats & get_instance_disk_info"