itest: ensure peer is connected befor channel open

After restarting the node, it will only actively connect to peers that
it has channels with. Since `assertChannelExistsAndClose` will close the
channels the node has with its peer right before shutdown, we cannot
guarantee that they are connected on start up and so need to actively
connect them.

itest/litd_firewall_test.go

@@ -1399,6 +1399,17 @@ func testChannelOpening(net *NetworkHarness, ht *harnessTest, t *testing.T) {
 
 	caveatCreds = metaDataInjector.addCaveat(caveat)
 
+	// Make sure to reconnect to Charlie after the restart.
+	_, err = lndConn2.ConnectPeer(
+		ctx, &lnrpc.ConnectPeerRequest{
+			Addr: &lnrpc.LightningAddress{
+				Pubkey: charlie.PubKeyStr,
+				Host:   charlie.Cfg.P2PAddr(),
+			},
+		}, caveatCreds,
+	)
+	require.NoError(t, err)
+
 	memoBefore := lastMemo
 	openResp, err = lndConn2.OpenChannelSync(
 		ctx, &lnrpc.OpenChannelRequest{