Allow to pass docker UCP image via env file

Related-Prod: PRODX-3456
Change-Id: I2f34e6912b108df68092ab29d8baed87e56ce861
diff --git a/de/heat-templates/fragments/SrvInstancesVM.yaml b/de/heat-templates/fragments/SrvInstancesVM.yaml
index f89e470..5d0c936 100644
--- a/de/heat-templates/fragments/SrvInstancesVM.yaml
+++ b/de/heat-templates/fragments/SrvInstancesVM.yaml
@@ -45,6 +45,9 @@
     type: string
   docker_ee_url:
     type: string
+  docker_ucp_image:
+    type: string
+    default: 'docker/ucp:3.2.4'
   hardware_metadata:
     description: The content of lab metadata.
     default: ''
@@ -72,6 +75,7 @@
             $private_floating_interface_ip: { get_attr: [private_floating_server_port, fixed_ips, 0, ip_address] }
             $private_floating_network_cidr: { get_param: private_floating_network_cidr }
             $functions_override: { get_param: functions_override }
+            $docker_ucp_image: { get_param: docker_ucp_image }
 
   inject_files:
     type: "OS::Heat::CloudConfig"