title: Override env values defined in container spec
body: <p>I have a configmap where I have defined the following key-value mapping in the <code>data</code> section:</p>
  
  <pre><code>apiVersion: v1
  kind: ConfigMap
  metadata:
    namespace: test
    name: test-config
  data:
    TEST: "CONFIGMAP_VALUE"
  </code></pre>
  
  <p>then in the definition of my container (in the deployment / statefulset manifest) I have the following:</p>
  
  <pre><code>        env:
          - name: TEST
            value: "ANOTHER_VALUE"
          envFrom:
          - configMapRef:
              name: test-config
  </code></pre>
  
  <p>When doing this I was expecting that the value from the configmap (TEST="CONFIGMAP_VALUE") will override the (default) value specified in the container spec (TEST="ANOTHER_VALUE"), but this is not the case (TEST always gets the value from the container spec). I couldn't find any relevant documentation about this - is it possible to achieve such env variable value overriding?</p>