Fix: coalesce.go warning while overriding the client affinity with a string value

[washtubs]

Create a local-values.yaml like the example shown in the values.yaml in the docs above client affinity:

client:
  affinity: |
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: node-role.kubernetes.io/master
            operator: DoesNotExist

If you run helm template -f ./local-values.yaml consul-test . | head, it will print a warning like so:

coalesce.go:196: warning: cannot overwrite table with non table for affinity (map[])

The end result is fine, but the warning is annoying. My understanding is when it's "coalescing" your local-values.yaml with the values.yaml it doesn't like it when a string is replacing an object.

Changes proposed in this PR:

• Default client affinity to null instead of an empty map prevents the coalesce.go warning from being printed

How I've tested this PR:

How I expect reviewers to test this PR:

Checklist:

• Bats tests added
• CHANGELOG entry added (HashiCorp engineers only, community PRs should not add a changelog entry)

[hashicorp-cla]

All committers have signed the CLA.

[ndhanushkodi]

@washtubs Can you sign the CLA? The change looks good to me.

[ndhanushkodi]

It looks good to me! On L754 we do the same with nodeSelector, where it's type is string and we default it to null, and seems reasonable to do the same here since it's not a map.

[washtubs]

Done!