Minor refactoring for Hyper-V utils and tests

Minor refactoring for Hyper-V utils and tests

A separate commit in the blueprint addressed by this patch
introduces the "_filter_acls" and "_create_acl" methods
which can be used in "enable_port_metrics_collection"
as well to reduce code duplication.

This commit eliminates also some code duplication
in test_hyperv_utilsv2.py.

Implements: blueprint hyperv-security-groups

Change-Id: I48fb5389b6049641ca2649990e81e94e4c45ef7f