pytest: fix flake in test_node_reannounce

Fixes 2569999 (pytest: fix flake in test_node_reannounce).

Converting ->set->list does not give deterministic order, so we can
end up with the two lists differing due to order:

```
 May send its own announcement *twice*, since it always spams us.
        msgs2 = list(set(msgs2))
>       assert msgs == msgs2
E       AssertionError: assert ['01012ff5580...000000000000'] == ['01014973d81...000000000000']
E         At index 0 diff: '01012ff55800f5b9492021372d74df4d6547bb0d32aec8d4c932a8c3b044e4bd983c429154e73091b0a2aff1cf9bbf16b37e6e9dd10ce4c2d949217366472acd341b0007800000080269a262bbd1750266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c035180266e453454e494f524245414d000000000000000000000000000000000000000000000000' != '01014973d8160dd8fc28e8fb25c40b9d5c68aed8dfb36af9fc13e4d2040fb3718553051a188ce98239c0bed138e1f8713a64acc7de98c183c9597fa58bf37f0b89bb0007800000080269a262bbd16c022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59022d2253494c454e544152544953542d336333626132392d6d6f6464656400000000000000'
E         Full diff:
E           [
E         +  '01012ff55800f5b9492021372d74df4d6547bb0d32aec8d4c932a8c3b044e4bd983c429154e73091b0a2aff1cf9bbf16b37e6e9dd10ce4c2d949217366472acd341b0007800000080269a262bbd1750266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c035180266e453454e494f524245414d000000000000000000000000000000000000000000000000',
E            '01014973d8160dd8fc28e8fb25c40b9d5c68aed8dfb36af9fc13e4d2040fb3718553051a188ce98239c0bed138e1f8713a64acc7de98c183c9597fa58bf37f0b89bb0007800000080269a262bbd16c022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59022d2253494c454e544152544953542d336333626132392d6d6f6464656400000000000000',
E         -  '01012ff55800f5b9492021372d74df4d6547bb0d32aec8d4c932a8c3b044e4bd983c429154e73091b0a2aff1cf9bbf16b37e6e9dd10ce4c2d949217366472acd341b0007800000080269a262bbd1750266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c035180266e453454e494f524245414d000000000000000000000000000000000000000000000000',
E           ]
``

Signed-off-by: Rusty Russell <[email protected]>

tests/test_gossip.py

@@ -1281,8 +1281,7 @@ def test_node_reannounce(node_factory, bitcoind, chainparams):
                             filters=['0109', '0107', '0102', '0100', '0012'])
 
     # May send its own announcement *twice*, since it always spams us.
-    msgs2 = list(set(msgs2))
-    assert msgs == msgs2
+    assert set(msgs) == set(msgs2)
     # Won't have queued up another one, either.
     assert not l1.daemon.is_in_log('node_announcement: delaying')
 
@@ -1308,8 +1307,7 @@ def test_node_reannounce(node_factory, bitcoind, chainparams):
                             # channel_announcement and channel_updates.
                             # And pings.
                             filters=['0109', '0107', '0102', '0100', '0012'])
-    msgs2 = list(set(msgs2))
-    assert msgs != msgs2
+    assert set(msgs) != set(msgs2)
 
 
 def test_gossipwith(node_factory):