Automatic merge from submit-queue (batch tested with PRs 54045, 51375). 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>.

Upgrade to go1.9

**What this PR does / why we need it**:
Upgrade to go1.9. Upgrading is good. It's "the best golang release ever"!

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #49484

**Special notes for your reviewer**:

**Release note**:

```release-note
Upgrade to go1.9
```

/assign @luxas @ixdy @wojtek-t