pytest: fix flake in test_onchain_different_fees()

We didn't wait until l2 processed the final state of HTLC #2, so
it might not include it when it drops onchain, leading to us only
getting 3 (not 4) sendrawtx calls.

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

tests/test_closing.py

@@ -1189,19 +1189,19 @@ def test_onchain_different_fees(node_factory, bitcoind, executor):
 
     l2.rpc.dev_ignore_htlcs(id=l1.info['id'], ignore=True)
     p1 = executor.submit(l1.pay, l2, 1000000000)
-    l1.daemon.wait_for_log('htlc 0: RCVD_ADD_ACK_COMMIT->SENT_ADD_ACK_REVOCATION')
+    l2.daemon.wait_for_log('htlc 0: SENT_ADD_ACK_COMMIT->RCVD_ADD_ACK_REVOCATION')
 
     l1.set_feerates((16000, 11000, 7500, 3750))
     p2 = executor.submit(l1.pay, l2, 900000000)
-    l1.daemon.wait_for_log('htlc 1: RCVD_ADD_ACK_COMMIT->SENT_ADD_ACK_REVOCATION')
+    l2.daemon.wait_for_log('htlc 1: SENT_ADD_ACK_COMMIT->RCVD_ADD_ACK_REVOCATION')
 
     # Restart with different feerate for second HTLC.
     l1.set_feerates((5000, 5000, 5000, 3750))
     l1.restart()
     l1.daemon.wait_for_log('peer_out WIRE_UPDATE_FEE')
 
     p3 = executor.submit(l1.pay, l2, 800000000)
-    l1.daemon.wait_for_log('htlc 2: RCVD_ADD_ACK_COMMIT->SENT_ADD_ACK_REVOCATION')
+    l2.daemon.wait_for_log('htlc 2: SENT_ADD_ACK_COMMIT->RCVD_ADD_ACK_REVOCATION')
 
     # Drop to chain
     l1.rpc.dev_fail(l2.info['id'])