@param cluster configuration to read
@param option which option to read
@param buf where to write the configuration value
@param len the size of buf in bytes
@returns 0 on success, negative error code on failure
@returns -ENAMETOOLONG if the buffer is too short to contain the
requested value
Get the value of a configuration option
@param cluster configuration to read @param option which option to read @param buf where to write the configuration value @param len the size of buf in bytes @returns 0 on success, negative error code on failure @returns -ENAMETOOLONG if the buffer is too short to contain the requested value