Change bash completion dir permissions to 0750

This is no reason for this dir to be world-readable.

Change-Id: I50e85b5bb6116c64535ecbf09718141086c703c5
(cherry picked from commit 5d2116e747)

cinderclient/base.py

@@ -273,7 +273,7 @@ class Manager(common_base.HookableMixin):
         cache_dir = os.path.expanduser(os.path.join(base_dir, uniqifier))
 
         try:
-            os.makedirs(cache_dir, 0o755)
+            os.makedirs(cache_dir, 0o750)
         except OSError:
             # NOTE(kiall): This is typically either permission denied while
             #              attempting to create the directory, or the directory