Add protect mode for new leader sync and commit binlog

[heroming]

For pika writing binlog and use consensus, master respond client SUCCESS just when command finish writing master's DB, but before slave receive next sync message, binlog will not write to slave's DB. Worse still, if master crash before next sync message send, all slave DB will not have the last data, and then one of slave become new master, we must waiting for all binlog write DB before respond to new command.