site.conf: set tunneldigger section arround mtu

Signed-off-by: Jan-Tarek Butt <tarek@ring0.de>

site.conf

@@ -43,6 +43,9 @@
 
 	mesh_vpn = {
 		enabled = true,
+		tunneldigger = {
+			mtu = 1312,
+		},
 		mtu = 1312,
 		-- The bandwidth limit can be enabled by default here.
 		bandwidth_limit = {