itest+lntest: fix itest re the new block driven behavior

lntest/harness.go

@@ -1579,14 +1579,20 @@ func (h *HarnessTest) CleanupForceClose(hn *node.HarnessNode) {
 	h.AssertNumPendingForceClose(hn, 1)
 
 	// Mine enough blocks for the node to sweep its funds from the force
-	// closed channel. The commit sweep resolver is able to broadcast the
-	// sweep tx up to one block before the CSV elapses, so wait until
-	// defaulCSV-1.
+	// closed channel. The commit sweep resolver is able to offer the input
+	// to the sweeper at defaulCSV-1, and broadcast the sweep tx once one
+	// more block is mined.
 	//
 	// NOTE: we might empty blocks here as we don't know the exact number
 	// of blocks to mine. This may end up mining more blocks than needed.
 	h.MineEmptyBlocks(node.DefaultCSV - 1)
 
+	// Assert there is one pending sweep.
+	h.AssertNumPendingSweeps(hn, 1)
+
+	// Mine a block to trigger the sweep.
+	h.MineEmptyBlocks(1)
+
 	// The node should now sweep the funds, clean up by mining the sweeping
 	// tx.
 	h.MineBlocksAndAssertNumTxes(1, 1)