Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Introduce e2e test for Stackdriver Metadata Agent

**What this PR does / why we need it**:
Introduce e2e test for Stackdriver Metadata Agent

**Release note**:
```release-note
None
```