clusterloader2: Avoid logging and awaiting waitgroup when chaosmonkey is disabled

[devodev]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Not really a bug but I noticed that the waitgroup returned from chaosMonkey.Init() is always non-nil and therefore we always log and await the waitgroup, which can be confusing when chaosmonkey nodekiller is disabled. I also updated to avoid emitting an empty log statement when the summary is empty.

I1219 14:48:15.653932   23514 simple_test_executor.go:80] Waiting for the chaos monkey subroutine to end...
I1219 14:48:15.653947   23514 simple_test_executor.go:82] Chaos monkey ended.
I1219 14:48:15.657172   23514 simple_test_executor.go:102] 

Which issue(s) this PR fixes:

None

Special notes for your reviewer:

None

[k8s-ci-robot]

Hi @devodev. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[marseel]

Thanks for contribution!

/ok-to-test
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: devodev, marseel

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