Fix host manager node detection logic

This is the last in a series of patches to prepare Ironic for the
removal of capabilities in Nova HostManager.

IronicHostManager 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 IronicHostManager to correctly
choose IronicHostState 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 has landed.

Change-Id: Ifa47d721835cfea87e9d0bce87c7853dd6724b98
Closes-Bug: #1260265
Merge "Fix host manager node detection logic"