Remove traces of now unused host capabilities from scheduler

Host capabilities updates are no longer used by the scheduler. All host
state is instead fetched from the DB. Some left over fields are still kept
by the host manager but contain no data. This change remove the last
traces of host capabilities from the scheduler.

The baremetal 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 (bug 1260265). The logic to
decide on host state class to use is updated to use DB data instead and
a test is added to verify the same.

Change-Id: I350109492c2addf5fdfaadee7cec4784f244e102
Closes-Bug: #1260265