Fix usage of Metadata classifier field in openolt adapter

// The classifierInfo[Metadata] carries the vlan that the OLT see when it receives packet from the ONU
if metadata, ok := classifierInfo[Metadata].(uint64); ok {
 vid := uint32(metadata)
 // Set the OVid or IVid classifier based on the whether OLT is using a transparent tag or not
 // If OLT is using transparent tag mechanism, then it classifies whatever tag it sees to/from ONU which
 //is OVid from the perspective of the OLT. When OLT also places or pops the outer tag, then classifierInfo[Metadata]
 // becomes the IVid.
 if classifier.OVid != 0 && classifier.OVid != ReservedVlan { // This is case when classifier.OVid is not set
 if vid != ReservedVlan {
 classifier.IVid = vid
 }
 } else {
 if vid != ReservedVlan {
 classifier.OVid = vid
 }
 }
}

	// Ignore Downlink trap flow given by core, cannot do anything with this flow */
	if vlan, exists := downlinkClassifier[VlanVid]; exists {
		if vlan.(uint32) == (uint32(ofp.OfpVlanId_OFPVID_PRESENT) | 4000) { //private VLAN given by core
			if metadata, exists := downlinkClassifier[Metadata]; exists { // inport is filled in metadata by core
				if uint32(metadata.(uint64)) == plt.MkUniPortNum(ctx, flowContext.intfID, flowContext.onuID, flowContext.uniID) {
					logger.Infow(ctx, "ignoring-dl-trap-device-flow-from-core",
						log.Fields{
							"flow":      flowContext.logicalFlow,
							"device-id": f.deviceHandler.device.Id,
							"onu-id":    flowContext.onuID,
							"intf-id":   flowContext.intfID})
					return nil
				}
			}
		}
	}