[Role API] When Update end point is called with an already existing role name, the update happens instead of returning 'already exists' message

[sdgun]

Steps
Call update end point for a role by changing the role name to another existing role name

Current behavior
Update happens

Expected behavior
Should not allow duplicate role names(create end point has this restriction)

[eisbilir]

@sdgun
I found the updated record:

The first "React Developer 2" role actually not exists in database.
I explained it here: #290 (comment)
Now after the above update, we actually have a "React Developer 2" Role.
When I try to update another Role's name to "React Developer 2" I get the error now:

@nikolay83
The undeleted record issue #290 caused this particular issue.
Our update endpoint follow the same not allow duplicate name restriction with create endpoint.
And it's not possible to create a new role with duplicate name because Role model has a uniqe name index.

[sdgun]

Verified with some more roles and update returned a proper message without letting to update role name to an existing role name.