lightningd: apply feerate changes correctly.

Feerate changes are asymmetric, as they can only be sent by the funder.

For FUNDER, the remote feerate is set when upon send of
commitment_signed, and the local feerate is set on receipt of
revoke_and_ack.

For non-funder, the local feerate is set on receipt of
commitment_signed, and the remote feerate set on send of
revoke_and_ack.  In our code, these two happen together.

channeld gets this right, but lightningd ignored the funder/fundee
distinction, and as a result, receipt of a commitment_signed by the
funder altered fees in the database.  If there was a reconnection
event or restart, then these (incorrect) values would be used, causing
us to complain about a 'Bad commit_sig signature' and close the
channel.

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

tests/test_connection.py

@@ -2148,7 +2148,6 @@ def test_feerate_spam(node_factory, chainparams):
         l1.daemon.wait_for_log('peer_out WIRE_UPDATE_FEE', timeout=5)
 
 
-@pytest.mark.xfail(strict=True)
 @unittest.skipIf(not DEVELOPER, "need dev-feerate")
 def test_feerate_stress(node_factory, executor):
     # Third node makes HTLC traffic less predictable.