Remove unnecessary reference to ARP thread.
Remove unnecessary reference to ARP thread.

gallenmu/MoonGen,dschoeffm/MoonGen,gallenmu/MoonGen,emmericp/MoonGen,gallenmu/MoonGen,emmericp/MoonGen,gallenmu/MoonGen,dschoeffm/MoonGen,scholzd/MoonGen,gallenmu/MoonGen,gallenmu/MoonGen,scholzd/MoonGen,scholzd/MoonGen,emmericp/MoonGen,gallenmu/MoonGen,gallenmu/MoonGen,dschoeffm/MoonGen