Simplify subtrees logic in kernel_route.
Simplify subtrees logic in kernel_route.

dtaht/babeld-shortrtt-metrics,tcatm/babeld,Drooids/babeld,wlanslovenija/babeld,sudomesh/babeld,wlanslovenija/babeld,jech/babeld,jech/babeld,Gwendocg/babeldToS,Gwendocg/babeldToS