test_lightningd.py: make sure l2 has seen announcements in test_gossip_jsonrpc

>       assert [c['active'] for c in l2.rpc.getchannels()['channels']] == [True, True]
E       AssertionError: assert [False, True] == [True, True]
E         At index 0 diff: False != True
E         Full diff:
E         - [False, True]
E         + [True, True]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_lightningd.py

@@ -1384,6 +1384,13 @@ class LightningDTests(BaseLightningDTests):
                                  'Channel {}\\(1\\) was updated.'
                                  .format(channel_id)])
 
+        l2.daemon.wait_for_logs(['peer_out WIRE_CHANNEL_ANNOUNCEMENT',
+                                 'peer_in WIRE_CHANNEL_ANNOUNCEMENT',
+                                 'Channel {}\\(0\\) was updated.'
+                                 .format(channel_id),
+                                 'Channel {}\\(1\\) was updated.'
+                                 .format(channel_id)])
+
         nodes = l1.rpc.getnodes()['nodes']
         assert set([n['nodeid'] for n in nodes]) == set([l1.info['id'], l2.info['id']])