multi: allow disable banning peers

When users set `gossip.ban-threshold` to 0, it's now treated as setting
the ban score to max uint64, which effectively disables the banning. We
still want to record the peer's ban score in case we need it for future
debugging.

discovery/gossiper_test.go

@@ -995,6 +995,7 @@ func createTestCtx(t *testing.T, startHeight uint32, isChanPeer bool) (
 		GetAlias:              getAlias,
 		FindChannel:           mockFindChannel,
 		ScidCloser:            newMockScidCloser(isChanPeer),
+		BanThreshold:          DefaultBanThreshold,
 	}, selfKeyDesc)
 
 	if err := gossiper.Start(); err != nil {
@@ -4656,7 +4657,7 @@ func TestChanAnnBanningNonChanPeer(t *testing.T) {
 	}
 
 	// Loop 100 times to get nodePeer banned.
-	for i := 0; i < 100; i++ {
+	for i := range DefaultBanThreshold {
 		// Craft a valid channel announcement for a channel we don't
 		// have. We will ensure that it fails validation by modifying
 		// the tx script.
@@ -4746,7 +4747,7 @@ func TestChanAnnBanningChanPeer(t *testing.T) {
 	nodePeer := &mockPeer{remoteKeyPriv1.PubKey(), nil, nil, atomic.Bool{}}
 
 	// Loop 100 times to get nodePeer banned.
-	for i := 0; i < 100; i++ {
+	for i := range DefaultBanThreshold {
 		// Craft a valid channel announcement for a channel we don't
 		// have. We will ensure that it fails validation by modifying
 		// the router.