Update Metadefs associated with ImagePropertiesFilter

From: http://docs.openstack.org/trunk/config-reference/content/section_compute-scheduler.html#imagepropertiesfilter

Filters hosts based on properties defined on the instance's image.

Updated descriptions to be provide better information.
Added baremetal "hypervisor_type" after getting info from
Nova core about what hypervisors to include.

Left out "architecture" for now, because horizon fails when
trying to update architecture property.

Change-Id: I9195825a0ab4b89e764983da06827173a2daa23c
Closes-bug: 1368965
(cherry picked from commit 236c9db4eb119dfaa6a592097b97e7b3f623a506)