storage: use 0711 as the default perms for dirs

There should be no need to make dir based pools world/group readable.
So use 0711, not 0755, as the default perms for storage dirs.

Updates in v2:
 - adapt commit wording to mention dropping group readable as well
Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>

docs/formatstorage.html.in

@@ -444,7 +444,7 @@
         namespace. It provides information about the permissions to use for the
         final directory when the pool is built. There are 4 child elements.
         The <code>mode</code> element contains the octal permission set.
-        The <code>mode</code> defaults to 0755 when not provided.
+        The <code>mode</code> defaults to 0711 when not provided.
         The <code>owner</code> element contains the numeric user ID.
         The <code>group</code> element contains the numeric group ID.
         If <code>owner</code> or <code>group</code> aren't specified when

src/storage/storage_util.h

@@ -138,7 +138,7 @@ int virStorageBackendVolOpen(const char *path, struct stat *sb,
     ATTRIBUTE_RETURN_CHECK
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
-# define VIR_STORAGE_DEFAULT_POOL_PERM_MODE 0755
+# define VIR_STORAGE_DEFAULT_POOL_PERM_MODE 0711
 # define VIR_STORAGE_DEFAULT_VOL_PERM_MODE  0600
 
 int virStorageBackendUpdateVolInfo(virStorageVolDefPtr vol,