Adds metrics collection support in Hyper-V

Blueprint: hyper-v-metrics

Hyper-V Server 2012 supports a new set of metrics API that can be used
to provide instance metrics data to external applications, e.g.
Ceilometer.

Metrics collection is disabled by default and can be enabled with a
config option.

Change-Id: I3523888c6bdd22f488c273c9e3eea1083a479700
Merge "Adds metrics collection support in Hyper-V"