Allow to deploy prometheus as standalone service

Now it is able to install proemtheus on host and
use it to scrape data from other prometheuses.

Prod-related: PROD-17350

Change-Id: I11d65920c0e9b685dead22a5551521fa15d13f25
diff --git a/metadata/service/relay/cluster.yml b/metadata/service/relay/cluster.yml
new file mode 100644
index 0000000..73c5e66
--- /dev/null
+++ b/metadata/service/relay/cluster.yml
@@ -0,0 +1,10 @@
+parameters:
+  prometheus:
+    relay:
+      backends:
+      - host: ${_param:cluster_node01_address}
+        port: ${_param:prometheus_server_bind_port}
+      - host: ${_param:cluster_node02_address}
+        port: ${_param:prometheus_server_bind_port}
+      - host: ${_param:cluster_node03_address}
+        port: ${_param:prometheus_server_bind_port}