bugfix: make setAnnotation do what the signature implies

[nammn]

• fix json readiness probe formatting.
• fix setAnnotation(object) to only set annotations to given object and not replace the whole object with the one backed by kubernetes. This was bugprone, especially since most of the places were relying on using calling setAnnotation(object.DeepCopy).
• fixes mongodConfig.DeepCopy since it was not null pointer safe.

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[lsierant]

Nice catch! LGTM!