Add missing stats info to BaremetalNodeState

This is the first of two patches to prepare baremetal for the removal
of capabilities in Nova HostManager.

BaremetalHostManager used to rely on capabilities info to decide which
host state class to use, VM or baremetal. This has been broken since
host capabilities reporting were removed in Nova, resulting in Nova
HostState class always being used.

BaremetalNodeState lacks stats info needed by some filters during
scheduling. This may result in failures like ComputeCapabilitiesFilter
not returning any hosts. This must be fixed before BaremetalNodeState
can be used again.

Change-Id: I63d992371640b2fd33d35eae72201fd41944f8a4
Partial-Bug: #1260265
Merge "Add missing stats info to BaremetalNodeState"