CA-147516: networkd fix for VLANs plus enic-workaround

When the "enic" workaround from 6b6c59c4 is in effect, we need to make sure
that VLAN names (for additional VLANs) are still constructed correctly, as usual.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Merge pull request #1964 from robhoes/ucs

CA-147516: networkd fix for VLANs plus enic-workaround