Bug#13414773 -INNODB_FAST_SHUTDOWN=2, ASSERT STATE == BUF_BLOCK_ZIP_PAGE

We can have dirty pages during a fast shutdown. Relax the assertion.

storage/innodb_plugin/buf/buf0buf.c

@@ -957,8 +957,10 @@ buf_pool_free(void)
 		ut_ad(bpage->in_LRU_list);
 
 		if (state != BUF_BLOCK_FILE_PAGE) {
-			/* We must not have any dirty block. */
-			ut_ad(state == BUF_BLOCK_ZIP_PAGE);
+			/* We must not have any dirty block except
+			when doing a fast shutdown. */
+			ut_ad(state == BUF_BLOCK_ZIP_PAGE
+			      || srv_fast_shutdown == 2);
 			buf_page_free_descriptor(bpage);
 		}