Apply proper mask on libvirt image files

PROD-28442

Change-Id: Ia70e8568c2eba57b685ad640c91e9a7935e7e866
diff --git a/metadata/service/control/virt.yml b/metadata/service/control/virt.yml
index 05e1591..8065707 100644
--- a/metadata/service/control/virt.yml
+++ b/metadata/service/control/virt.yml
@@ -2,6 +2,7 @@
   salt:
     control:
       enabled: true
+      file_mask: 022
       virt_enabled: true
       size:
         small: