Controller drops foreign OwnerReferences

[wonderhoss]

When reconciling a SealedSecret where the corresponding Secret already exists in the cluster, the controller will replace that Secret with a fresh copy, overwriting any existing ObjectMeta.

This drops all existing OwnerReferences on the Secret and causes other controllers in the same cluster to misbehave where they rely on these OwnerReferences to be present.
Our Wave Controler uses OwnerReferences to tie Secrets to Deployments that use them and fails to correctly track Secrets that are also owned by a SealedSecret.

The problematic code is at

sealed-secrets/cmd/controller/controller.go

Lines 192 to 194 in 2e3902b

	if err != nil && errors.IsAlreadyExists(err) {
	_, err = c.sclient.Secrets(ssecret.GetObjectMeta().GetNamespace()).Update(secret)
	}

where Update() is called without merging with existing OwnerReferences first.

I'm currently working on a PR to fix this.

[wonderhoss]

@anguslees See #130