Low: mysql: add a new paramater "client_timeout"

Currently, a timeout for the MySQL client is hard coded in the mysql RA and users can not change timeout from "10" seconds.
This MySQL client's timeout coused operations error whatever user set a long timeout for operations.
A "client_timeout" parameter make it possible to set a arbitrary timeout for the MySQL client that appropriate to operations timeout.
The default value is 0(timeout is disabled, and the MySQL client waits for response from the MySQL server until the operation timeout is occurred).