checks version of deployment matches version go file

[matzew]

Task:

Change the controller to look for the serving.knative.dev/release label in the manifest and use that to set the status.version in the CR.

Add a test for that too

[matzew]

/assign @matzew

[matzew]

/assign @aliok

[knative-prow-robot]

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/assign @aliok

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[aliok]

I will do the same thing in knative/eventing-operator#42