BUG: Not able to create a super user

[JenySadadia]

Observed a couple of issues while registering a super user with is_superuser=1 flag in the request dictionary.

Request command:

curl -X 'POST' 'http://localhost:8001/latest/user/register' -H 'accept: application/json'   -H 'Content-Type: application/json'  -H 'Authorization: Bearer TOKEN' -d '{"username": "test_admin", "email": "[email protected]", "password": "admin", "is_superuser": 1, "groups": ["kernelci"]}'

API logs:

kernelci-api          | User 674572be9c8d350bbb789ad7 test_admin has registered.
kernelci-api          | exception: update must either be a list or an instance of dict, bson.son.SON, or any other type that inherits from collections.Mapping
kernelci-api          | INFO:     172.18.0.1:41080 - "POST /latest/user/register HTTP/1.1" 500 Internal Server Error

This request generates a regular user account instead of a super user.