Create deletePort(bridge,port) on OVSDB

The current deletePort(port) method in OvsdbBridgeConfig deletes a port for all the bridges in the OVSDB instance, it's better to mimic the implementation of sudo ovs-vsctl delete-port and specify also a bridge on which to delete the port.
the new method signature will be deletePort(BridgeName b, PortDescription p)
This will be the parallel of addPort method.