network: introduce 'degraded-carrier' operstate to order all states

Previously, 'degraded' state is ambiguous for bonding or bridge master:
1. one or more slave interfaces does not have carrier,
2. no link local address is assigned to the master,
3. combination of the above two.

This makes the above case 1 and 3 are in the new 'degraded-carrier'
state, and makes 'degraded' state as all slaves are active but no
link local address on master.

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

@@ -1200,7 +1200,7 @@ class NetworkdNetWorkBondTests(unittest.TestCase, Utilities):
 
         output = subprocess.check_output(['networkctl', 'status', 'bond99']).rstrip().decode('utf-8')
         print(output)
-        self.assertRegex(output, 'State: degraded \(configured\)')
+        self.assertRegex(output, 'State: degraded-carrier \(configured\)')
 
         self.assertEqual(subprocess.call(['ip', 'link', 'set', 'dummy98', 'up']), 0)
         time.sleep(2)
@@ -1313,7 +1313,7 @@ class NetworkdNetWorkBridgeTests(unittest.TestCase, Utilities):
         time.sleep(3)
 
         output = subprocess.check_output(['networkctl', 'status', 'bridge99']).rstrip().decode('utf-8')
-        self.assertRegex(output, 'State: degraded \(configured\)')
+        self.assertRegex(output, 'State: degraded-carrier \(configured\)')
 
         self.assertEqual(subprocess.call(['ip', 'link', 'del', 'dummy98']), 0)
         time.sleep(3)