Artifact is wrongly reported in storage after a restart

[stefanprodan]

The status of all sources are reporting as ArtifactInStorage=True even if the storage is empty because the controller pod was deleted. This is due to the fact that we don't write to the status once we observe a drift, making the consumers (Kustomize and Helm controller) miss behave. Ref: https://github.com/fluxcd/source-controller/issues/935