Fix linting errors in the errlist package

References influxdata#4098

cmd/influx_tools/internal/errlist/errlist.go

@@ -9,24 +9,28 @@ type ErrorList struct {
 	errs []error
 }
 
+// NewErrorList returns an empty *ErrorList
 func NewErrorList() *ErrorList {
 	return &ErrorList{errs: make([]error, 0)}
 }
 
+// Add appends an error to the error list if the it not nil
 func (el *ErrorList) Add(err error) {
 	if err == nil {
 		return
 	}
 	el.errs = append(el.errs, err)
 }
 
+//Err returns whether or not an error list is an error.
 func (el *ErrorList) Err() error {
 	if len(el.errs) == 0 {
 		return nil
 	}
 	return el
 }
 
+// Error satisfies the error interface.
 func (el *ErrorList) Error() string {
 	var buf bytes.Buffer
 	for _, err := range el.errs {