rails g scaffold_controller --skip_namespace expectation

Hi.

```
$ rails g scaffold_controller Admin::User
```

I expected to create such code.

```ruby
class Admin::UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]

  def index
    @users = User.all
  end
```

But It created

```ruby
class Admin::UsersController < ApplicationController
  before_action :set_admin_user, only: [:show, :edit, :update, :destroy]

  def index
    @admin_users = Admin::User.all
  end
```

I searched '--skip-namespace' specification.
But I could not find it.

I suggest the --skip-namespace behavior this pull request.

Thanks.