MDEV-29905 fixup: Remove some unnecessary code

srv_shutdown(): Do not call log_free_check(), because it will now
be repeatedly called by ibuf_merge_all(). Do not call
srv_sync_log_buffer_in_background(), because we do not actually care
about durability during shutdown. Log writes will already be triggered
by buf_flush_page_cleaner() for writing back modified pages, possibly by
log_free_check().

logs_empty_and_mark_files_at_shutdown(): Clean up a condition.
This function is the caller of srv_shutdown(), and it will ensure that
the log and the buffer pool will be in clean state before shutdown.

storage/innobase/log/log0log.cc

@@ -1096,13 +1096,9 @@ ATTRIBUTE_COLD void logs_empty_and_mark_files_at_shutdown()
 	}
 
 	/* We need these threads to stop early in shutdown. */
-	const char* thread_name;
-
-   if (srv_fast_shutdown != 2 && trx_rollback_is_active) {
-		thread_name = "rollback of recovered transactions";
-	} else {
-		thread_name = NULL;
-	}
+	const char* thread_name = srv_fast_shutdown != 2
+		&& trx_rollback_is_active
+		? "rollback of recovered transactions" : nullptr;
 
 	if (thread_name) {
 		ut_ad(!srv_read_only_mode);

storage/innobase/srv/srv0srv.cc

@@ -1677,13 +1677,8 @@ void srv_shutdown(bool ibuf_merge)
 		n_tables_to_drop = row_drop_tables_for_mysql_in_background();
 
 		if (ibuf_merge) {
-			srv_main_thread_op_info = "checking free log space";
-			log_free_check();
 			srv_main_thread_op_info = "doing insert buffer merge";
 			n_bytes_merged = ibuf_merge_all();
-
-			/* Flush logs if needed */
-			srv_sync_log_buffer_in_background();
 		}
 
 		/* Print progress message every 60 seconds during shutdown */