This patch imitates the ML2/OVS Trunk driver behaviour. When the
trunk parent port is bound:
* A new trunk cannot be created using this parent port.
* If the port is assigned as parent port of a trunk, this
trunk cannot be deleted.
Closes-Bug: #2022059
Change-Id: I8cfa7e67524a42224cbb4b3c3cec3cfa49b795fd