Send ok packet to client earlier

Currently the ok packet to a MariaDB server client is sent in dispatch_command() by the call
thd->protocol->end_statement()

We can improve the response time between MariaDB server and client by sending the result packet earlier.

For select queries we could do that in bool select_send::send_eof().
For update queries we could do that at once the commit has been approved.

This will improve performance as the client will be able to process the return data earlier
and send it's next query while the server is doing cleanup of the previous query.