This change sets the ResourceVersion on the PrometheusRule object before
it is updated in Kubernetes.
This change fixes the following error
```
is invalid: metadata.resourceVersion: Invalid value: 0x0: must be specified for an update
```
which can occur during update when no ResourceVersion is set.
Resolves#4528
Signed-off-by: Alexander Trost <galexrt@googlemail.com>