Fix BaremetalHostManager node detection logic

This is the second patch 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.

This patch fixes the detection logic in BaremetalHostManager to
correctly choose BaremetalHostState class for use with baremetal nodes.
Tests are added to verify that the correct class is used for both vm
and baremetal nodes.

In reality, the new detection logic will not start to deliver the
correct HostState class until the Nova HostManager change that follows
has landed.

Change-Id: I0c2e6d985fb29f35b823cdf9a83fead2fa45082a
Partial-Bug: #1260265
Merge "Fix BaremetalHostManager node detection logic"