parameterize the db image name

Author: bparees

openshift/templates/django-postgresql.json

@@ -249,7 +249,7 @@
             "containers": [
               {
                 "name": "postgresql",
-                "image": "openshift/postgresql-92-centos7",
+                "image": "${POSTGRESQL_IMAGE}",
                 "ports": [
                   {
                     "containerPort": 5432
@@ -327,6 +327,11 @@
       "generate": "expression",
       "from": "[a-zA-Z0-9]{16}"
     },
+    {
+      "name": "POSTGRESQL_IMAGE",
+      "description": "Image to use for postgresql",
+      "value": "openshift/postgresql-92-centos7"      
+    },
     {
       "name": "APP_CONFIG",
       "description": "Relative path to Gunicorn configuration file (optional)"