Standardized signing_dir in configs

While debugging API noticed the following error when starting cinder.
    2013-10-21 15:57:43.793 4789 WARNING keystoneclient.middleware.auth_token [-] signing_dir mode is 0755 instead of 0700
I know we are not using PKI, but the configs should be standardized with proper
owner/modes.
Merge pull request #81 from blueboxgroup/blueboxgroup/signing-dir

Standardized signing_dir in configs