Fixes bug: 1153274
Due to a bug in setting up external ports the Hyper-V agent fails to work in
scenarios with VLAN and flat networks.
Furthermore, a warning message on Hyper-V 2012 indicates that external
port settings are ignored. As a result the agent can be simplified by
avoiding vswitch external ports configurations.
Change-Id: I860d22f427cb10dbeac422c1db2b3bcf9e84150f