Support configuring ONU to not add/remove C-VLAN tags

No matter whether FTTH or FTTB, the subscriber should be able to be identified by a logical port and so multiple logical ports of the same logical device should be able to work with the same or different S-Tags.
This issue is for the case when the CPE itself sends a C-VLAN tagged packet.
S-VLAN tags should be able to be supported to identify the subscriber without using C-VLANs on the same or a different PON port of asfvolt16 OLT (this including the case where the same C-VLANs are used).