rapl_collector: fix issue with invalid metric name (#2299)

Signed-off-by: Andrei Neagoe <3854672+aneagoe@users.noreply.github.com>

collector/rapl_linux.go

@@ -80,7 +80,7 @@ func (c *raplCollector) Update(ch chan<- prometheus.Metric) error {
 		index := strconv.Itoa(rz.Index)
 
 		descriptor := prometheus.NewDesc(
-			prometheus.BuildFQName(namespace, "rapl", rz.Name+"_joules_total"),
+			prometheus.BuildFQName(namespace, "rapl", SanitizeMetricName(rz.Name+"_joules_total")),
 			"Current RAPL "+rz.Name+" value in joules",
 			[]string{"index", "path"}, nil,
 		)