Add comments about the order of authenticators (#256)
Add comments about the order of authenticators (#256)

Automatic merge from submit-queue

Add comments about the order of authenticators

**Release note**:

```
NONE
```
/assign @myidpt
frankbu/istio,smawson/istio,frankbu/istio,smawson/istio,frankbu/istio,istio/istio,sebastienvas/istio,istio/istio,mandarjog/istio,frankbu/istio,frankbu/istio,geeknoid/istio,geeknoid/istio,smawson/istio,mandarjog/istio,smawson/istio,sebastienvas/istio,geeknoid/istio,mandarjog/istio,istio/istio,smawson/istio,smawson/istio,frankbu/istio,geeknoid/istio,sebastienvas/istio,sebastienvas/istio,sebastienvas/istio,geeknoid/istio,geeknoid/istio,istio/istio,istio/istio,mandarjog/istio,mandarjog/istio