zones: fix PruneWireguardConfig recursion

Zones and Zone implementation should call Machine's directly
instead jumping back to Zone's for each Machine again and again

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/zones/wireguard.go

@@ -45,7 +45,7 @@ func pruneWireguardConfig(m MachineIterator, ring int) error {
 	var err error
 
 	m.ForEachMachine(func(p *Machine) bool {
-		err = p.zone.PruneWireguardConfig(ring)
+		err = p.PruneWireguardConfig(ring)
 		if os.IsNotExist(err) {
 			// ignore
 			err = nil