test-network: add test for macvlan BroadcastQueueMulticastLength= and BroadcastQueueThreashold=

test/test-network/conf/21-macvlan.netdev

@@ -3,3 +3,7 @@
 Name=macvlan99
 Kind=macvlan
 MTUBytes=2000
+
+[MACVLAN]
+BroadcastMulticastQueueLength=1234
+BroadcastQueueThreshold=2147483647

test/test-network/systemd-networkd-tests.py

@@ -1640,6 +1640,8 @@ class NetworkdNetDevTests(unittest.TestCase, Utilities):
                 print(output)
                 self.assertIn(' mtu 2000 ', output)
                 self.assertIn(f' macvlan mode {mode} ', output)
+                self.assertIn(' bcqueuelen 1234 ', output)
+                self.assertIn(' bclim 2147483647 ', output)
 
     @expectedFailureIfModuleIsNotAvailable('ipvlan')
     def test_ipvlan(self):