Fix the problem that the device can not be added to default_user

Fix the problem that the device can not be added to default_user

- Problem: Unable to add device to default_user.
- Cause: ua-manager regards default_user's ID is always 1.
  However, If ua-manager has a problem occurred while accessing user-db,
  so all user information is deleted. In this case the user id of the default user
  is added to a value that is not 1.
- Solution: Deletes the hard-coded default user ID is 1.

Change-Id: I0d79364107aa7416c5b64b9481d2edc83801fbc4
Signed-off-by: saerome.kim <saerome.kim@samsung.com>