ntpq input: ignore lines that are '-'

closes #1223

plugins/inputs/ntpq/ntpq.go

@@ -122,6 +122,9 @@ func (n *NTPQ) Gather(acc telegraf.Accumulator) error {
 				if index == -1 {
 					continue
 				}
+				if fields[index] == "-" {
+					continue
+				}
 
 				if key == "when" {
 					when := fields[index]
@@ -169,6 +172,9 @@ func (n *NTPQ) Gather(acc telegraf.Accumulator) error {
 				if index == -1 {
 					continue
 				}
+				if fields[index] == "-" {
+					continue
+				}
 
 				m, err := strconv.ParseFloat(fields[index], 64)
 				if err != nil {