Low: RA: mysql: correctly advertise "additional_parameters" parameter (LF 2320)
Low: RA: mysql: correctly advertise "additional_parameters" parameter (LF 2320)

Was advertised as integer, really expected a string. Change parameter
type to string.
Also, fix a small typo in the parameter description.

stevenraspudic/resource-agents,asp24/resource-agents,stevenraspudic/resource-agents,stevenraspudic/resource-agents,asp24/resource-agents,asp24/resource-agents