tm revamp: address review comments

Signed-off-by: Sugu Sougoumarane <ssougou@gmail.com>

go/vt/vttablet/tabletmanager/rpc_actions.go

@@ -94,7 +94,7 @@ func (agent *ActionAgent) changeTypeLocked(ctx context.Context, tabletType topod
  }
 
  // let's update our internal state (stop query service and other things)
- // refreshTablet will runHealthCheck.
+ // refreshTablet will invoke broadcastHealth if needed.
  if err := agent.refreshTablet(ctx, "ChangeType"); err != nil {
  return err
  }