multi: add new config QuiescenceTimeout

This commit makes removes the `defaultQuiescenceTimeout` and makes it
configurable as different nodes have different network environment. In
addition the default timeout has been increased from 30s to 60s.

config.go

@@ -751,6 +751,7 @@ func DefaultConfig() Config {
 		Sweeper: lncfg.DefaultSweeperConfig(),
 		Htlcswitch: &lncfg.Htlcswitch{
 			MailboxDeliveryTimeout: htlcswitch.DefaultMailboxDeliveryTimeout,
+			QuiescenceTimeout:      lncfg.DefaultQuiescenceTimeout,
 		},
 		GRPC: &GRPCConfig{
 			ServerPingTime:    defaultGrpcServerPingTime,