Needs to be set on the imagestream, not the imagestreamtag.

roles/openshift-apps/greenwave/files/imagestream.yml

@@ -2,3 +2,13 @@ apiVersion: v1
 kind: ImageStream
 metadata:
   name: "greenwave"
+{% if env == 'staging' %}
+spec:¬
+  tags:¬
+  - name: latest¬
+    importPolicy:¬
+      scheduled: true¬
+    from:¬
+      kind: DockerImage¬
+      name: quay.io/factory2/greenwave:latest
+{% endif %}

roles/openshift-apps/greenwave/templates/imagestreamtag.yml

@@ -1,19 +0,0 @@
-- apiVersion: v1
-  generation: 5
-  kind: ImageStreamTag
-  lookupPolicy:
-    local: false
-  metadata:
-    creationTimestamp: null
-    name: greenwave:latest
-  tag:
-    annotations: null
-    from:
-      kind: DockerImage
-      name: quay.io/factory2/greenwave:latest
-    generation: 5
-    importPolicy:
-      scheduled: true
-    name: latest
-    referencePolicy:
-      type: Source