pytest: Fix test_fee_limits

This was flaky because we didn't wait for the fee update to complete
and were using the old, way too small, fees, which upset bitcoind.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

tests/test_lightningd.py

@@ -2880,6 +2880,11 @@ class LightningDTests(BaseLightningDTests):
         l3.daemon.wait_for_log('peer_in WIRE_UPDATE_FEE')
         l3.daemon.wait_for_log('peer_in WIRE_COMMITMENT_SIGNED')
 
+        # We need to wait untill both have committed and revoked the
+        # old state, otherwise we'll still try to commit with the old
+        # 15sat/byte fee
+        l1.daemon.wait_for_log('peer_out WIRE_REVOKE_AND_ACK')
+
         # Now shutdown cleanly.
         l1.rpc.close(l3.info['id'])
         l1.daemon.wait_for_log('-> CLOSINGD_COMPLETE')