MDEV-14180 fixup: Avoid unnecessary dirtying of pages

fil_crypt_rotate_page(): If a page is already marked as dirty,
do not move it in buf_pool.flush_list. Actual re-encryption
will happen in buf_flush_page(), and moving the page in
buf_pool.flush_list may only postpone the operation.

storage/innobase/fil/fil0crypt.cc

@@ -1820,6 +1820,9 @@ fil_crypt_rotate_page(
 		if (block->page.status == buf_page_t::FREED) {
 			/* Do not modify freed pages to avoid an assertion
 			failure on recovery.*/
+		} else if (block->page.oldest_modification()) {
+			/* Do not unnecessarily touch pages that are
+			already dirty. */
 		} else if (space->is_stopping()) {
 			/* The tablespace is closing (in DROP TABLE or
 			TRUNCATE TABLE or similar): avoid further access */