Set 755 on Prometheus config dir explicitly

Change-Id: Ic69a796135557e0d4c5b7d56f2938522f266ae4c
Closes-Bug: PROD-31032
(cherry picked from commit 7158ea54e465a5d4bab428566c30ca8e8ef30d45)
diff --git a/prometheus/server.sls b/prometheus/server.sls
index da4378c..8262c0b 100644
--- a/prometheus/server.sls
+++ b/prometheus/server.sls
@@ -5,6 +5,7 @@
   file.directory:
     - name: {{ server.dir.config }}
     - makedirs: True
+    - mode: 755
 
 prometheus_server_data_dir:
   file.directory: