During a deploy, if keystone Fernet key rotation happens before the
keystone container starts, the rotation may fail with 'permission
denied'. This happens because config.json for Keystone sets the
permissions for /etc/keystone/fernet-keys.
This change fixes the issue by also setting the permissions for
/etc/keystone/fernet-keys in config.json for keystone-fernet and
keystone-ssh.
Change-Id: I561e4171d14dcaad8a2a9a36ccab84a670daa904
Closes-Bug: #1888512
b45679f122