heat loadbalancer : make LB nested template create credentials

Create User/AccessKey resources correctly in the LB nested template
so we can create a cfn-credentials file which will allow cfn-hup
to access the CFN API

fixes bug 1131663

Change-Id: I11b6640dbc5689de8f6103f4c1e841f42acbba54
Merge "heat loadbalancer : make LB nested template create credentials"