Change hardcoded nightly repo to variable

Change-Id: Ifbe7369ddc2937f8abd406eb7097a67d5373c863
diff --git a/linux/system/repo_local/grafana.yml b/linux/system/repo_local/grafana.yml
index a94d1be..f2d9ad5 100644
--- a/linux/system/repo_local/grafana.yml
+++ b/linux/system/repo_local/grafana.yml
@@ -4,6 +4,6 @@
       repo:
         grafana:
           refresh_db: ${_param:linux_repo_refresh_db}
-          source: "deb [arch=amd64] http://${_param:local_repo_url}/ubuntu-${_param:linux_system_codename}/ nightly grafana"
+          source: "deb [arch=amd64] http://${_param:local_repo_url}/ubuntu-${_param:linux_system_codename}/ ${_param:apt_mk_version} grafana"
           architectures: amd64
           key_url: "http://${_param:local_repo_url}/public.gpg"