K8S_NAMESPACE -> ACK_SYSTEM_NAMESPACE

This is the patch that corresponds to changes made to ACK runtime to
rename the `K8S_NAMESPACE` environment variable to
`ACK_SYSTEM_NAMESPACE` to better represent what this variable referred
to.

Related: aws-controllers-k8s/runtime#72
Related: aws-controllers-k8s/community#1178
Issue: aws-controllers-k8s/community#1173

Signed-off-by: Jay Pipes <jaypipes@gmail.com>

Author: jaypipes

templates/config/controller/deployment.yaml.tpl

@@ -49,7 +49,7 @@ spec:
             cpu: 100m
             memory: 200Mi
         env:
-        - name: K8S_NAMESPACE
+        - name: ACK_SYSTEM_NAMESPACE
           valueFrom:
             fieldRef:
               fieldPath: metadata.namespace

templates/helm/templates/deployment.yaml

@@ -57,7 +57,7 @@ spec:
         resources:
           {{- toYaml .Values.resources | nindent 10 }}
         env:
-        - name: K8S_NAMESPACE
+        - name: ACK_SYSTEM_NAMESPACE
           valueFrom:
             fieldRef:
               fieldPath: metadata.namespace