Remove the VtepBinding.create() override.

Removes the create() method override for VtepBinding Python MidoNet
Client since the GET Rest API on VtepBinding has been implemented. It
is necessary for VtepBinding.delete() to work correctly.

Fix MN-1824
Merge pull request #171 from midokura/dev/tomohiko/mn-1824-vtep-binding-delete/20140528

Remove the VtepBinding.create() override.