Fix incorrect port numbers being registered for services on macOS.

Per https://developer.apple.com/documentation/dnssd/1804733-dnsserviceregister,
DNSServiceRegister() takes the port number in network byte order. This fixes the
bug with wrong ports being registered on macOS.

zeroconf/src/macos/service_ref.rs

@@ -56,7 +56,7 @@ impl ManagedDNSServiceRef {
                 regtype,
                 domain,
                 host,
-                port,
+                port.to_be(),
                 txt_len,
                 txt_record,
                 callback,