GIT-331: fix shadowing key from the kv pair

[harshanarayana]

What this PR does / why we need it:
While trying to take a stab at #275 I noticed that there is a lingering issue in the KVListFormat function in terms of how it processes the keys

klog/internal/serialize/keyvalues.go

Lines 112 to 118 in 9c48b7d

	if k, ok := k.(string); ok {
	// Avoid one allocation when the key is a string, which
	// normally it should be.
	b.WriteString(k)
	} else {
	b.WriteString(fmt.Sprintf("%s", k))
	}

In case if the key passed to the KVListFormat is not of string type, this ends up consuming the key and only printing the value.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #331

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

Non string keys are displayed as string formatted keys

[pohly]

/lgtm

Good find, thanks.

[pohly]

/assign @serathius

For approval.

[dims]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dims, harshanarayana, pohly

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