Fixing default config lookup for bookshelves_view_type in BookshelfController

[philjak]

A wrong setting key (bookshelf_view_type) was used. So the configured default in .env was not used. This PR fixes this issue.

How to reproduce:

• Set APP_VIEWS_BOOKSHELVES=list in .env File
• Use a new user and open a random bookshelf (/shelves/{slug})

Expected: See books as list.

What actually happens: Default grid view is shown.

[ssddanbrown]

Thanks for offering a PR @philjak but this was not a bug or incorrect value used; Those are two different views with two different preference keys. There's currently no .env option for the default shelf view option.

[philjak]

@ssddanbrown Ahh, ok. Sorry. I just recognized that the default behavior changed during the last updates