Fix host manager node detection logic

The Ironic host manager used to rely on capabilities info to decide
which host state class to use, VM or baremetal. This has been broken
since host capabilities were removed from Nova. The logic to decide
on host state class is updated to now use values from the db and
tests are added to validate this.

Change-Id: Ifa47d721835cfea87e9d0bce87c7853dd6724b98
Closes-Bug: #1260265
Closes-Bug: #1326312