VOL-2894 - reference the voltha GRPC end point via a holder

Change-Id: If24299556ad6cacf9cd0f793167a2c908534729c
(cherry picked from commit f8ce7d2ceaf5c37cc992448e7c6b6331a234168b)
diff --git a/internal/pkg/openflow/client.go b/internal/pkg/openflow/client.go
index 94ad645..ab884da 100644
--- a/internal/pkg/openflow/client.go
+++ b/internal/pkg/openflow/client.go
@@ -22,13 +22,15 @@
 	"encoding/binary"
 	"encoding/json"
 	"errors"
-	"github.com/donNewtonAlpha/goloxi"
-	ofp "github.com/donNewtonAlpha/goloxi/of13"
-	"github.com/opencord/voltha-lib-go/v3/pkg/log"
-	"github.com/opencord/voltha-protos/v3/go/voltha"
 	"io"
 	"net"
 	"time"
+
+	"github.com/donNewtonAlpha/goloxi"
+	ofp "github.com/donNewtonAlpha/goloxi/of13"
+	"github.com/opencord/ofagent-go/internal/pkg/holder"
+	"github.com/opencord/voltha-lib-go/v3/pkg/log"
+	"github.com/opencord/voltha-protos/v3/go/voltha"
 )
 
 var NoVolthaConnectionError = errors.New("no-voltha-connection")
@@ -87,7 +89,7 @@
 	OFControllerEndPoint string
 	Port                 uint16
 	DeviceID             string
-	VolthaClient         voltha.VolthaServiceClient
+	VolthaClient         *holder.VolthaServiceClientHolder
 	PacketOutChannel     chan *voltha.PacketOut
 	ConnectionMaxRetries int
 	ConnectionRetryDelay time.Duration