* image-dired.el: Don't use find-file for temporary work.

* image-dired.el: Don't use find-file for temporary work.
(image-dired--with-db-file): New macro.
(image-dired-write-tags, image-dired-remove-tag)
(image-dired-create-gallery-lists, image-dired-write-comments)
(image-dired-get-comment, image-dired-mark-tagged-files)
(image-dired-list-tags, image-dired-gallery-generate): Use it.
(image-dired-gallery-generate): Use insert-file-contents.