lntest+itest: remove the usage of ht.AssertActiveHtlcs

The method `AssertActiveHtlcs` is now removed due to it's easy to be
misused. To assert a given htlc, use `AssertOutgoingHTLCActive` and
`AssertIncomingHTLCActive` instead for ensuring the HTLC exists in the
right direction. Although often the case `AssertNumActiveHtlcs` would be
enough as it implicitly checks the forwarding behavior for an
intermediate node by asserting there are always num_payment*2 HTLCs.

itest/lnd_hold_invoice_force_test.go

@@ -50,8 +50,12 @@ func testHoldInvoiceForceClose(ht *lntest.HarnessTest) {
 
 	// Once the HTLC has cleared, alice and bob should both have a single
 	// htlc locked in.
-	ht.AssertActiveHtlcs(alice, payHash[:])
-	ht.AssertActiveHtlcs(bob, payHash[:])
+	//
+	// Alice should have one outgoing HTLCs on channel Alice -> Bob.
+	ht.AssertOutgoingHTLCActive(alice, chanPoint, payHash[:])
+
+	// Bob should have one incoming HTLC on channel Alice -> Bob.
+	ht.AssertIncomingHTLCActive(bob, chanPoint, payHash[:])
 
 	// Get our htlc expiry height and current block height so that we
 	// can mine the exact number of blocks required to expire the htlc.