🌱 Improve reconcile state logs (don't log empty diff)

[sbueringer]

Signed-off-by: Stefan Büringer buringerst@vmware.com

What this PR does / why we need it:
Currently we get a few logs like this in our e2e tests

{"ts":1722858941941.0283,"caller":"cluster/reconcile_state.go:317","msg":"Patching DockerMachineTemplate/quick-start-itkrd6-ks4hk, diff: {}","controller":"topology/cluster","controllerGroup":"cluster.x-k8s.io","controllerKind":"Cluster","Cluster":{"name":"quick-start-itkrd6","namespace":"quick-start-k6hnu4"},"namespace":"quick-start-k6hnu4","name":"quick-start-itkrd6","reconcileID":"da094763-efac-489d-9df5-9c518faa3e18","resource":{"group":"infrastructure.cluster.x-k8s.io","version":"v1beta1","resource":"DockerMachineTemplate"},"DockerMachineTemplate":{"name":"quick-start-itkrd6-ks4hk","namespace":"quick-start-k6hnu4"},"v":0}

This PR ensures that an empty diff is returned as "" instead of "{}" so our log statements are omitting the diff entirely

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 #

[sbueringer]

/assign @chrischdi

[sbueringer]

/test ?

[k8s-ci-robot]

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• /test pull-cluster-api-e2e-conformance-main
• /test pull-cluster-api-e2e-main
• /test pull-cluster-api-e2e-mink8s-main
• /test pull-cluster-api-e2e-upgrade-1-30-1-31-main
• /test pull-cluster-api-test-main
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• /test pull-cluster-api-apidiff-main

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/test ?

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[sbueringer]

/test pull-cluster-api-e2e-conformance-ci-latest-main
/test pull-cluster-api-e2e-conformance-main
/test pull-cluster-api-e2e-main
/test pull-cluster-api-e2e-mink8s-main
/test pull-cluster-api-e2e-upgrade-1-30-1-31-main

[sbueringer]

/cherry-pick release-1.8

[k8s-infra-cherrypick-robot]

@sbueringer: once the present PR merges, I will cherry-pick it on top of release-1.8 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.8

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[chrischdi]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 142dfd615752a770e651cb4ec065ceb4bb014d7d

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrischdi

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[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #11015

In response to this:

/cherry-pick release-1.8

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.