Fix __get_managed_instance_group_for_instance (issue #13)
Fix __get_managed_instance_group_for_instance (issue #13)

Added variable initialization.
Added just in case, as normally this service will be activated during sysprep, which means there is at least one item in the metadata.
GoogleCloudPlatform/gce-automated-ad-join,GoogleCloudPlatform/gce-automated-ad-join