AddPath capability related code path should only used when capability is present

  This code previously failed to remove and therefore withdraw routes from
  non AddPathRX capable neighbors as there could no PathID be found for them.

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

routingtable/adjRIBOut/adj_rib_out.go

@@ -111,14 +111,19 @@ func (a *AdjRIBOut) RemovePath(pfx bnet.Prefix, p *route.Path) bool {
 	}
 
 	a.rt.RemovePath(pfx, p)
-	pathID, err := a.pathIDManager.releasePath(p)
-	if err != nil {
-		log.Warningf("Unable to release path: %v", err)
-		return true
+
+	// If the neighbar has AddPath capabilities, try to find the PathID
+	if a.neighbor.CapAddPathRX {
+		pathID, err := a.pathIDManager.releasePath(p)
+		if err != nil {
+			log.Warningf("Unable to release path for prefix %s: %v", pfx.String(), err)
+			return true
+		}
+
+		p = p.Copy()
+		p.BGPPath.PathIdentifier = pathID
 	}
 
-	p = p.Copy()
-	p.BGPPath.PathIdentifier = pathID
 	a.removePathFromClients(pfx, p)
 	return true
 }