[Bug]: the value of data_dir isn't accuracy

[longdafeng]

Please check the issue list for the same bug

• I have checked issue list and this bug is encountered for the first time.

Environment

- OB Version&commit_id or other module version&commit_id (e.g. observer V3.1.2 8b23a93):
- Hardware parameter:OS type & Compliler & CPU etc. 
- Others

observer version: V3.1.3

Fast Reproduce Steps(Required)

dir_data参数值不准确，可以通过
show variables like '%data_dir%';
来查看

Actual Behavior

显示为/usr/local/mysql/data

Expected Behavior

显示为ob实际data file使用的目录

other information

来源：贵州双龙 https://open.oceanbase.com/ask/detail?id=20400117

[hnwyllmm]

已修正