MDEV-21054 Crash on shutdown due to btr_search_latches=NULL

innodb_shutdown(): Invoke os_aio_free() before btr_search_sys_free().

storage/innobase/srv/srv0start.cc

@@ -2385,17 +2385,11 @@ void innodb_shutdown()
 	}
 
 	dict_sys.close();
-	btr_search_sys_free();
-
-	/* 3. Free all InnoDB's own mutexes and the os_fast_mutexes inside
-	them */
 	os_aio_free();
+	btr_search_sys_free();
 	row_mysql_close();
 	srv_free();
 	fil_system.close();
-
-	/* 4. Free all allocated memory */
-
 	pars_lexer_close();
 	recv_sys.close();