multi: ensure all lnwallet.LightningChannel's are stopped

This commit ensures that we always clean up the resources that are
created when a new instance of a lnwallet.LightningChannel is
instantiated. The is necessary due to the sigPool that’s now present as
an internal goroutine.

fundingmanager.go

@@ -1090,6 +1090,7 @@ func (f *fundingManager) waitForFundingConfirmation(completeChan *channeldb.Open
 		fndgLog.Errorf("error creating new lightning channel: %v", err)
 		return
 	}
+	defer channel.Stop()
 
 	// Next, we'll send over the funding locked message which marks that we
 	// consider the channel open by presenting the remote party with our

rpcserver.go

@@ -563,6 +563,7 @@ func (r *rpcServer) CloseChannel(in *lnrpc.CloseChannelRequest,
 		if err != nil {
 			return err
 		}
+		defer channel.Stop()
 
 		_, bestHeight, err := r.server.cc.chainIO.GetBestBlock()
 		if err != nil {