Rename prometheus relay image

Change-Id: I9f232ab28388e9aebd8e0edfe8cfbef3c8513e3c
Related-PROD: PROD-31454
diff --git a/defaults/docker_images.yml b/defaults/docker_images.yml
index b1bbce0..41f161e 100644
--- a/defaults/docker_images.yml
+++ b/defaults/docker_images.yml
@@ -34,7 +34,7 @@
     docker_image_prometheus: "${_param:mcp_docker_registry}/openstack-docker/prometheus:${_param:mcp_version}"
     docker_image_prometheus_gainsight: "${_param:mcp_docker_registry}/openstack-docker/gainsight:${_param:mcp_version}"
     docker_image_prometheus_gainsight_elasticsearch: "${_param:mcp_docker_registry}/openstack-docker/gainsight_elasticsearch:${_param:mcp_version}"
-    docker_image_prometheus_relay: "${_param:mcp_docker_registry}/openstack-docker/prometheus_relay:${_param:mcp_version}"
+    docker_image_prometheus_relay: "${_param:mcp_docker_registry}/openstack-docker/prometheus-relay:${_param:mcp_version}"
     docker_image_pushgateway: "${_param:mcp_docker_registry}/openstack-docker/pushgateway:${_param:mcp_version}"
     docker_image_remote_agent: "${_param:mcp_docker_registry}/openstack-docker/telegraf:${_param:mcp_version}"
     docker_image_remote_collector: "${_param:mcp_docker_registry}/openstack-docker/heka:${_param:mcp_version}"