Update IronicHostManager tests to better match how code works

This is the first 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.

IronicBareMetal tests make use of an internal Nova HostManager variable
in a way that hides the fact that IronicNodeState class is no longer
used. This patch rewrites tests to better reflect how Ironic/Nova code
now works and prepares for further changes that needs to land in Ironic
before Nova HostManager capabilities can be removed.

Change-Id: I795eaed58f6587585d89366d8f1e521588866a58
Partial-Bug: #1260265
Merge "Update IronicHostManager tests to better match how code works"