Fixes missing host in Hyper-V get_volume_connector

Fixes bug: #1215765

The Hyper-V driver is not returning the host in the
"get_volume_connector" method.

This commit fixes the issue by adding the "host" key to the dictionary
returned by the method.

Adds also a unit test for get_volume_connector.

Change-Id: Ic74882e54994f957bf6d2bb75bbd53c6a346042e
Merge "Fixes missing host in Hyper-V get_volume_connector"