Fix deadlock in monitor

monitor/service.go

@@ -166,11 +166,11 @@ type RemoteWriterConfig struct {
 
 // SetPointsWriter can be used to set a writer for the monitoring points.
 func (m *Monitor) SetPointsWriter(pw PointsWriter) error {
-	m.mu.Lock()
 	if !m.storeEnabled {
 		// not enabled, nothing to do
 		return nil
 	}
+	m.mu.Lock()
 	m.PointsWriter = pw
 	m.mu.Unlock()