smb: extend smb share metrics (#1765)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/collector/system/system.go

@@ -139,7 +139,7 @@ func (c *Collector) Collect(ch chan<- prometheus.Metric) error {
 		return fmt.Errorf("failed to collect System metrics: %w", err)
 	}
 
-	data, ok := perfData[perfdata.EmptyInstance]
+	data, ok := perfData[perfdata.InstanceEmpty]
 	if !ok {
 		return errors.New("query for System returned empty result set")
 	}