Fix rabbitmq/meta/prometheus.yml for the CI

Change-Id: Iad37166d70bf3bbefa74d62c822061c1b3781471
diff --git a/metadata.yml b/metadata.yml
index 0ac0c26..7a18114 100644
--- a/metadata.yml
+++ b/metadata.yml
@@ -1,3 +1,6 @@
 name: "rabbitmq"
 version: "0.2"
 source: "https://github.com/salt-formulas/salt-formula-rabbitmq"
+dependencies:
+- name: linux
+  source: "https://github.com/salt-formulas/salt-formula-linux"