[ticket/11145] Wrong error thrown when uploading a bigger image.

When attaching an image to a post with a size larger than maximum defined in
php.ini, 'ATTACHED_IMAGE_NOT_IMAGE' error is thrown. $file->is_image() is
returning false value when image size is too large. Therefore, moved
not image test down after image size test.

PHPBB3-11145
Merge remote-tracking branch 'erangamapa/ticket/11145' into develop-olympus

* erangamapa/ticket/11145:
  [ticket/11145] Wrong error thrown when uploading a bigger image.
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/11145] Wrong error thrown when uploading a bigger image.
[ticket/11586] Combine administrator/moderator checks together.

PHPBB3-11586
[ticket/11586] Use a variable for $cat_id == ATTACHMENT_CATEGORY_IMAGE.

PHPBB3-11586
[ticket/11586] Combine $filedata['post_attach'] assign into a single statement.

PHPBB3-11586
[ticket/11586] Move $filedata['thumbnail'] to where it might be returned.

PHPBB3-11586
Merge remote-tracking branch 'bantu/ticket/11586' into develop

* bantu/ticket/11586:
  [ticket/11586] Move $filedata['thumbnail'] to where it might be returned.
  [ticket/11586] Combine $filedata['post_attach'] assign into a single statement.
  [ticket/11586] Use a variable for $cat_id == ATTACHMENT_CATEGORY_IMAGE.
  [ticket/11586] Combine administrator/moderator checks together.
[ticket/11538] Add admin as admins leader and moderator in memberlist_test

Removing the admin user from the admin and moderator group in memberlist_test
potentially breaks other tests, i.e. the ucp groups test.

PHPBB3-11538
Merge remote-tracking branch 'marc1706/ticket/11538' into develop

* marc1706/ticket/11538:
  [ticket/11538] Add admin as admins leader and moderator in memberlist_test