itest: fix flake in testSweepHTLCs

We need to make sure Caarol finishes settling her invoice with Bob
before shutting down, so we make sure `AssertHTLCNotActive` on Bob
happens before shutting node Carol.

Author: yyforyongyu

itest/lnd_sweep_test.go

@@ -864,13 +864,13 @@ func testSweepHTLCs(ht *lntest.HarnessTest) {
 	// Carol settles the first invoice.
 	carol.RPC.SettleInvoice(preimageSettled[:])
 
+	// Bob should have settled his outgoing HTLC with Carol.
+	ht.AssertHTLCNotActive(bob, bcChanPoint, payHashSettled[:])
+
 	// Let Carol go offline so we can focus on testing Bob's sweeping
 	// behavior.
 	ht.Shutdown(carol)
 
-	// Bob should have settled his outgoing HTLC with Carol.
-	ht.AssertHTLCNotActive(bob, bcChanPoint, payHashSettled[:])
-
 	// We'll now mine enough blocks to trigger Bob to force close channel
 	// Bob->Carol due to his outgoing HTLC is about to timeout. With the
 	// default outgoing broadcast delta of zero, this will be the same