PMM-13054 refactor the for loop

managed/services/supervisord/logs.go

@@ -273,7 +273,6 @@ func (l *Logs) victoriaMetricsTargets(ctx context.Context) ([]byte, error) {
 func readLog(name string, readLines int) ([]byte, time.Time, error) {
 	var (
 		m         time.Time
-		res       []byte
 		lineCount int
 	)
 	f, err := os.Open(name) //nolint:gosec
@@ -298,10 +297,10 @@ func readLog(name string, readLines int) ([]byte, time.Time, error) {
 		lineCount = readLines
 	}
 
-	res = make([]byte, 0)
+	res := []byte{}
 
 	reader := bufio.NewReader(f)
-	for lineCount >= 0 {
+	for {
 		b, err := reader.ReadBytes('\n')
 		if err == io.EOF {
 			// A special case when the last line does not end with a new line
@@ -321,6 +320,10 @@ func readLog(name string, readLines int) ([]byte, time.Time, error) {
 			// Do not decrease the counter for unlimited line count
 			lineCount--
 		}
+
+		if lineCount == 0 {
+			break
+		}
 	}
 
 	return res, m, nil