need to capture stdout too because of accesslog adapter (#965)
need to capture stdout too because of accesslog adapter (#965)

Automatic merge from submit-queue

need to capture mixer stdout too because of accesslog adapter

only applies to perf testing env, capture stdout too which is now where the mixer accesslog goes
avoids flooding the console / reduces slow down

```release-note
NONE
```
sebrandon1/istio,sebrandon1/istio,sebrandon1/istio,sebrandon1/istio