pytest: don't wait for channel active message in test_closing.py::test_penalty_htlc_tx_timeout

It might have already happened, and anyway, we wait for the actual state
below.

```
        # make database snapshot of l2
        l2.stop()
        l2_db_path = os.path.join(l2.daemon.lightning_dir, chainparams['name'], 'lightningd.sqlite3')
        l2_db_path_bak = os.path.join(l2.daemon.lightning_dir, chainparams['name'], 'lightningd.sqlite3.bak')
        copyfile(l2_db_path, l2_db_path_bak)
        l2.start()
        sync_blockheight(bitcoind, [l2])

        # push some money from l3->l2, so that the commit counter advances
        l2.rpc.connect(l3.info['id'], 'localhost', l3.port)
>       l2.daemon.wait_for_log('now ACTIVE')

tests/test_closing.py:908:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
contrib/pyln-testing/pyln/testing/utils.py:288: in wait_for_log
    return self.wait_for_logs([regex], timeout)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <pyln.testing.utils.LightningD object at 0x7f0c145a32d0>
regexs = ['now ACTIVE'], timeout = 60

    def wait_for_logs(self, regexs, timeout=TIMEOUT):
        """Look for `regexs` in the logs.

        We tail the stdout of the process and look for each regex in `regexs`,
        starting from last of the previous waited-for log entries (if any).  We
        fail if the timeout is exceeded or if the underlying process
        exits before all the `regexs` were found.

        If timeout is None, no time-out is applied.
        """
        logging.debug("Waiting for {} in the logs".format(regexs))
        exs = [re.compile(r) for r in regexs]
        start_time = time.time()
        pos = self.logsearch_start
        while True:
            if timeout is not None and time.time() > start_time + timeout:
                print("Time-out: can't find {} in logs".format(exs))
                for r in exs:
                    if self.is_in_log(r):
                        print("({} was previously in logs!)".format(r))
>               raise TimeoutError('Unable to find "{}" in logs.'.format(exs))
E               TimeoutError: Unable to find "[re.compile('now ACTIVE')]" in logs.

contrib/pyln-testing/pyln/testing/utils.py:264: TimeoutError
```

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

tests/test_closing.py

@@ -905,7 +905,7 @@ def test_penalty_htlc_tx_timeout(node_factory, bitcoind, chainparams):
 
     # push some money from l3->l2, so that the commit counter advances
     l2.rpc.connect(l3.info['id'], 'localhost', l3.port)
-    l2.daemon.wait_for_log('now ACTIVE')
+
     inv = l3.rpc.invoice(10**4, '1', 'push')
     # Make sure gossipd in l2 knows it's active
     wait_for(lambda: [c['active'] for c in l2.rpc.listchannels(l2.get_channel_scid(l3))['channels']] == [True, True])