Adds spec for Hyper-V disk latency metrics
Adds spec for Hyper-V disk latency metrics

https://blueprints.launchpad.net/ceilometer/+spec/hyper-v-disk-latency-metrics

Change-Id: I9f4a78dd75b87e5e243e214d1c0958ff63fcc4b1

openstack/telemetry-specs,openstack/ceilometer-specs