[5.3] Fix column overlaping on withCount

[fernandobandeira]

Fixes #16645

$roles = $user->roles()->withCount('permissions')->get()

Current wrong result for this function:

{
    "id": 4,
    "name": "Administrator",
    "description": "Some description here",
    "created_at": "2016-12-20 22:53:47",
    "updated_at": "2016-12-20 22:53:47",
    "role_id": "2",
    "user_id": "9",
    "permissions_count": "4",
    "pivot": {
        "user_id": "9",
        "role_id": "2"
    }
}

New result:

{
    "id": 2,
    "name": "Administrator",
    "description": "Some description here",
    "created_at": "2016-12-20 22:53:47",
    "updated_at": "2016-12-20 22:53:47",
    "permissions_count": "4",
    "pivot": {
        "user_id": "9",
        "role_id": "2"
    }
}

Notice the ID changed and it removed the inner join columns from the query, they are inside the pivot only now...
4 is the id of the role_user table, it was replacing the id of the role generating a wrong result for this query...

Repo for testing purposes:
https://github.com/cabalopolis/with-count-bug.

Not sure maybe we should target 5.4...

[fernandobandeira]

Ping @cabalopolis, @KKSzymanowski

[KKSzymanowski]

@fernandobandeira I'll take a look tomorrow morning.