bug: Case insensitive check failed

[Prnyself]

For some field, like Status in RulesType, it is marked as case insensitive in doc.

However, when check validation in code, only lower case values will be marked as valid. Here is the code.

// Validate validates the Rules.
func (v *RulesType) Validate() error {
	...
	if v.Status != nil {
		statusValidValues := []string{"enabled", "disabled"}
		statusParameterValue := fmt.Sprint(*v.Status)

		statusIsValid := false
		for _, value := range statusValidValues {
			if value == statusParameterValue {
				statusIsValid = true
			}
		}

		if !statusIsValid {
			return errors.ParameterValueNotAllowedError{
				ParameterName:  "Status",
				ParameterValue: statusParameterValue,
				AllowedValues:  statusValidValues,
			}
		}
	}
	...
}

See https://github.com/qingstor/qingstor-sdk-go/blob/master/service/bucket.go#L814 for more details.