Fixes Hyper-V 2008 R2 agent VLAN Settings issue

This issue affects Hyper-V 2008 R2 and does not affect
Hyper-V 2012 and above.

Hyper-V agent now also sets the vswitch external port's
DesiredEndpointMode to TRUNKED and adds the vlan_id in
the external port's TrunkedVLANList.

Change-Id: I632054ad15f33b13616f6fbbe4a637391ba8d374
Closes-Bug: #1361211

Conflicts:
	neutron/tests/unit/hyperv/test_hyperv_neutron_agent.py