[tools/circle_plus_gen] Fix type bug

[zetwhite]

Before

• m.name is sometimes bytes(when reading it from file) and sometimes string(set it from json file).
• This problem sometimes makes an error message
  • AttributeError: 'str' object has no attribute 'decode'

After

• m.name always bytes type

ONE-DCO-1.0-Signed-off-by: seunghui youn sseung.youn@samsung.com