Controller error "the object has been modified"

[ansd]

Describe the bug

When creating a new RabbitMQ cluster, sporadically, the controller logs show:

2020-11-17T09:07:28.109Z	ERROR	controller	Reconciler error	{"reconcilerGroup": "rabbitmq.com", "reconcilerKind": "RabbitmqCluster", "controller": "rabbitmqcluster", "name": "example", "namespace": "default", "error": "Operation cannot be fulfilled on rabbitmqclusters.rabbitmq.com \"example\": the object has been modified; please apply your changes to the latest version and try again"}
github.com/go-logr/zapr.(*zapLogger).Error
	/go/pkg/mod/github.com/go-logr/[email protected]/zapr.go:128
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:246
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:218
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).worker
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:197
k8s.io/apimachinery/pkg/util/wait.BackoffUntil.func1
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:155
k8s.io/apimachinery/pkg/util/wait.BackoffUntil
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:156
k8s.io/apimachinery/pkg/util/wait.JitterUntil
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:133
k8s.io/apimachinery/pkg/util/wait.Until
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:90

To Reproduce

Deploy RabbitMQ a couple of times

for i in $(seq 0 19); do kubectl rabbitmq create "rabbitmq-$i"; done

and check the controller logs.

Version information

• RabbitMQ Cluster Operator: latest main: 60f24b8
• Kubernetes: 1.19

Additional context

Understand why we see these errors.
Are we missing clientretry.RetryOnConflict somewhere or do we need to adapt the Backoff parameters?