Set auth_encryption_key option to be secret
Set auth_encryption_key option to be secret

To avoid exposure in the logs, auth_encryption_key from heat.conf
should be marked secret.

Change-Id: Ia4aca067f03317dd8073988cd29d26c2ccc88778
Closes-Bug: #1446408

maestro-hybrid-cloud/heat,miguelgrinberg/heat,maestro-hybrid-cloud/heat,miguelgrinberg/heat,dims/heat,openstack/heat,jasondunsmore/heat,dragorosson/heat,cryptickp/heat,pratikmallya/heat,srznew/heat,rh-s/heat,dims/heat,rh-s/heat,cryptickp/heat,takeshineshiro/heat,gonzolino/heat,cwolferh/heat-scratch,noironetworks/heat,gonzolino/heat,openstack/heat,pshchelo/heat,dragorosson/heat,steveb/heat,pshchelo/heat,rdo-management/heat,steveb/heat,srznew/heat,pratikmallya/heat,rdo-management/heat,noironetworks/heat,jasondunsmore/heat,cwolferh/heat-scratch,takeshineshiro/heat