Reduce lifecycle logging verbosity (#10)

This change reduces the reporter lifecycle logging message to
debug-level criticity, as it is annoying for software that use the
reporter to pollute its logs with unnecessary messages in nominal
situation.

root.go

@@ -59,17 +59,17 @@ func (r *Reporter) Start() error {
 // Stop will stop reporting and clean the associated resources.
 func (r *Reporter) Stop() error {
  if r.sentry != nil {
- r.Info("shutting down Sentry subsystem")
+ r.Debug("shutting down Sentry subsystem")
  r.sentry.Wait()
  r.sentry.Close()
  }
  if r.metrics != nil {
- r.Info("shutting down metric subsystem")
+ r.Debug("shutting down metric subsystem")
  err := r.metrics.Stop()
  if err != nil {
  _ = r.Error(err, "fail to stop the metric reporter")
  }
  }
- r.Info("stop reporting")
+ r.Debug("stop reporting")
  return nil
 }