Add OSSN-0014 - Cinder drivers set insecure file permissions

This adds OSSN-0014, which covers the introduction of files with liberal
access permissions by multiple Cinder drivers in OpenStack Icehouse and
earlier. Users with access to the Cinder host and processes running
on the Cinder host can exploit the file permissions to disclose,
modify, and/or destroy user block storage data.

Closes-Bug: 1260679
Change-Id: I4ac9e746401051d85cb9cfbcad3c88b04f23106c
Merge "Add OSSN-0014 - Cinder drivers set insecure file permissions"