Allow running with no interfaces given on command line.
Allow running with no interfaces given on command line.

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