Fix dropwizard parsing error for metrics that need escaped (#4142)

If the dropwizard parser cannot convert the metric name into a valid
line protocol series then we will accept the name as is.

(cherry picked from commit 0af40a8a5d)

metric/metric.go

@@ -202,6 +202,10 @@ func (m *metric) RemoveField(key string) {
 	}
 }
 
+func (m *metric) SetTime(t time.Time) {
+	m.tm = t
+}
+
 func (m *metric) Copy() telegraf.Metric {
 	m2 := &metric{
 		name:      m.name,