Add functionality that allow changing user's name

Add functionality that allow changing user's name

- Problem: Users want to change their name.
- Cause: it is not supported to change the user name once user information
  added to ua-manager DB.
- Solution: Make the user can change his name even user-information added.

Change-Id: I54901e5c24da13239e8cce7d35063d15ed6ca975
Signed-off-by: saerome.kim <saerome.kim@samsung.com>