Automatic merge from submit-queue (batch tested with PRs 61453, 61393, 61379, 61373, 61494). 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>.

Make `test-cmd` work with OS-X tooling

OS-X thips with the BSD versions of `date` and `grep`. Those don't have
certain features the script relies on:
- BSD date does not support nanoseconds (`%N`)
- BSD grep does not support perl RegEx (`-P`)

As we use `bash` specifically in the hashbang anyway it is probably fine
to rely on the `$RANDOM` bashism here.

**What this PR does / why we need it**:

Currently `make test-cmd` doesn't work on OSX. This PR makes `make test-cmd` work on OSX.

**Release note**:
```release-note
`make test-cmd` now works on OSX.
```

cc: @apelisse