Fixes missing method in Hyper-V Utils (Metering)

This cherry-picked commit is different from the original one because
the missing method was already added and merged into stable/havana
through another bug fix. (https://review.openstack.org/#/c/83222/)

This patch is meant to contain unit tests only.

Closes-Bug: #1252712
(cherry picked from commit 7af673ef1a348a21ea9751d8a271cb4ba74926fe)

Change-Id: I2beecfd13617fb243008016b810f49db5593fc65
Merge "Fixes missing method in Hyper-V Utils (Metering)" into stable/havana
Merge branch 'stable/havana' of https://github.com/openstack/quantum into havana/stable