Fixes Hyper-V agent issue with mixed network types

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
Merge "Fixes Hyper-V agent issue with mixed network types"