存储FLOAT类型，小数位数会扩展

[pengpeng176]

Environment:

• OS: [e.g. Ubuntu 18.04]
• CPU: [e.g. Intel Xeon xxxx]
• TuGraph-DB Version [e.g. 3.3.0]
  

Describe the bug

tugraph客户端执行CREATE (n:pp{id:1,float:1.2,double:1.2}) RETURN n
节点展示{"identity":0,"label":"pp","properties":{"double":1.2,"float":1.2000000476837158,"id":1}}