Add key to on change updates (#138)

### Why I did it

Key is missing in on change updates

Current:

root@efb973f6ce02:~# python /root/gnxi/gnmi_cli_py/py_gnmicli.py -g -t X -p 50051 -m subscribe -x NEIGH_STATE_TABLE -xt STATE_DB -o ndastreamingservertest --subscribe_mode 0 --submode 1 --interval 0 --update_count 2 --create_connections 1

```
2023-07-20 22:05:25.146156 response received: 
sync_response: true

2023-07-20 22:05:31.271959 response received: 
update {
  timestamp: 1689890731162239986
  prefix {
    target: "STATE_DB"
  }
  update {
    path {
      elem {
        name: "NEIGH_STATE_TABLE"
      }
    }
    val {
      json_ietf_val: "{\"peerType\":\"e-BGP\",\"state\":\"Active\"}"
    }
  }
}
```

Changed:

```
2023-07-20 22:01:56.251096 response received: 
sync_response: true

2023-07-20 22:02:15.558270 response received: 
update {
  timestamp: 1689890542962488225
  prefix {
    target: "STATE_DB"
  }
  update {
    path {
      elem {
        name: "NEIGH_STATE_TABLE"
      }
    }
    val {
      json_ietf_val: "{\"10.0.0.57\":{\"peerType\":\"e-BGP\",\"state\":\"Active\"}}"
    }
  }
}
```
#### How I did it

Set use key value to true

#### How to verify it

E2E test (sonic-mgmt test case)

gnmi_server/server_test.go

@@ -3438,6 +3438,26 @@ func TestClient(t *testing.T) {
     s.s.Stop()
 }
 
+func TestTableData2MsiUseKey(t *testing.T) {
+    tblPath := sdc.CreateTablePath("STATE_DB", "NEIGH_STATE_TABLE", "|", "10.0.0.57")
+    newMsi := make(map[string]interface{})
+    sdc.TableData2Msi(&tblPath, true, nil, &newMsi)
+    newMsiData, _ := json.MarshalIndent(newMsi, "", "  ")
+    t.Logf(string(newMsiData))
+    expectedMsi := map[string]interface{} {
+        "10.0.0.57": map[string]interface{} {
+            "peerType": "e-BGP",
+	    "state": "Established",
+        },
+    }
+    expectedMsiData, _ := json.MarshalIndent(expectedMsi, "", "  ")
+    t.Logf(string(expectedMsiData))
+
+    if !reflect.DeepEqual(newMsi, expectedMsi) {
+        t.Errorf("Msi data does not match for use key = true")
+    }
+}
+
 func TestGnmiSetBatch(t *testing.T) {
 	mockCode := 
 `

sonic_data_client/db_client.go

@@ -82,6 +82,15 @@ var IntervalTicker = func(interval time.Duration) <-chan time.Time {
 var NeedMock bool = false
 var intervalTickerMutex sync.Mutex
 
+func CreateTablePath(dbName string, tableName string, delimitor string, tableKey string) tablePath {
+	var tblPath tablePath
+	tblPath.dbName = dbName
+	tblPath.tableName = tableName
+	tblPath.delimitor = delimitor
+	tblPath.tableKey = tableKey
+	return tblPath
+}
+
 // Define a new function to set the IntervalTicker variable
 func SetIntervalTicker(f func(interval time.Duration) <-chan time.Time) {
 	if NeedMock == true {
@@ -687,11 +696,11 @@ func emitJSON(v *map[string]interface{}) ([]byte, error) {
 	return j, nil
 }
 
-// tableData2Msi renders the redis DB data to map[string]interface{}
+// TableData2Msi renders the redis DB data to map[string]interface{}
 // which may be marshaled to JSON format
 // If only table name provided in the tablePath, find all keys in the table, otherwise
 // Use tableName + tableKey as key to get all field value paires
-func tableData2Msi(tblPath *tablePath, useKey bool, op *string, msi *map[string]interface{}) error {
+func TableData2Msi(tblPath *tablePath, useKey bool, op *string, msi *map[string]interface{}) error {
 	redisDb := Target2RedisDb[tblPath.dbNamespace][tblPath.dbName]
 
 	var pattern string
@@ -805,7 +814,7 @@ func tableData2TypedValue(tblPaths []tablePath, op *string) (*gnmipb.TypedValue,
 			}
 		}
 
-		err := tableData2Msi(&tblPath, useKey, nil, &msi)
+		err := TableData2Msi(&tblPath, useKey, nil, &msi)
 		if err != nil {
 			return nil, err
 		}
@@ -1064,7 +1073,7 @@ func dbSingleTableKeySubscribe(c *DbClient, rsd redisSubData, updateChannel chan
 			} else if subscr.Payload == "hset" {
 				//op := "SET"
 				if tblPath.tableKey != "" {
-					err = tableData2Msi(&tblPath, false, nil, &newMsi)
+					err = TableData2Msi(&tblPath, false, nil, &newMsi)
 					if err != nil {
 						enqueueFatalMsg(c, err.Error())
 						return
@@ -1076,7 +1085,7 @@ func dbSingleTableKeySubscribe(c *DbClient, rsd redisSubData, updateChannel chan
 						continue
 					}
 					tblPath.tableKey = subscr.Channel[prefixLen:]
-					err = tableData2Msi(&tblPath, false, nil, &newMsi)
+					err = TableData2Msi(&tblPath, true, nil, &newMsi)
 					if err != nil {
 						enqueueFatalMsg(c, err.Error())
 						return
@@ -1185,7 +1194,7 @@ func dbTableKeySubscribe(c *DbClient, gnmiPath *gnmipb.Path, interval time.Durat
 		}
 		log.V(2).Infof("Psubscribe succeeded for %v: %v", tblPath, subscr)
 
-		err = tableData2Msi(&tblPath, false, nil, &msiAll)
+		err = TableData2Msi(&tblPath, false, nil, &msiAll)
 		if err != nil {
 			handleFatalMsg(err.Error())
 			return