Neutron keystone-signing dir should be 0700...

The permissions on the signing dir should be 0700 not 0770.

This fixes a WARN message from auth_token:

 keystoneclient.middleware.auth_token [-] signing_dir mode is 0770
 instead of 0700

Change-Id: Ie67a97ba9ba21b1bb2aa184a3aa37063ac08b6c1
Merge "Neutron keystone-signing dir should be 0700..."