UNI trap flows created by flow decomposer are incomplete

Ponsim is not trapping DHCP packets to the controller (SEBA-269). 

For UNI trap flows, VOLTHA's flow decomposer adds a rule to the OLT that matches packets with vlan_vid = UNI port ID.  This assumes that the packets have already been tagged with this VLAN by the ONU.

In Ponsim there is a low priority default rule to tag packets with vlan_vid = UNI port ID.  In SiaB, once EAPOL authentication happens, a higher priority rule is added that pushes the c-tag as the vlan_vid.  As a result the DHCP request packets are tagged with the c-tag and don't match the trap rule at the OLT.

I believe a reasonable solution is for the flow decomposer to add a rule to both the OLT and ONU for each UNI trap flow.  The ONU rule will tag packets intended to be trapped at the OLT with a VLAN of the UNI port ID.  These packets will then match the trap rule on the OLT.