bug #2762: Generate BRIDGE as "onebr<vlanid>" if vlan_id is defined

(cherry picked from commit d1ea5db93c2683727f408d920bdae9c95308ef47)
bug #2762: Prevent collitions between vlanid and vnetid

(cherry picked from commit ad1276927c8d6089f240a7bd8cf43f4ae7e57d96)