Merge pull request kubernetes#48384 from atlassian/update-testify

Automatic merge from submit-queue (batch tested with PRs 49017, 45440, 48384, 45894, 48808)

Update two dependencies

**What this PR does / why we need it**:
github.com/stretchr/testify - main desired update. Old version has bugs. Specifically I encountered stretchr/testify#347 which was fixed a year ago.

github.com/davecgh/go-spew/spew is set to the newest version, a bit
newer than required by testify. Updated from version 6 Nov 2015 to
27 Jun 2017.

github.com/stretchr/objx is not updated - testify uses version
from 27 May 2014 which is older than 28 Sep 2015 used now (latest
actually). In practice there is only a tiny difference - one method was
removed in new version.

**Release note**:

```release-note
NONE
```
/sig testing

Author: Kubernetes Submit Queue