heat engine : loadbalancer resource template, refer to StackId

Use the new AWS::StackId pseudo parameter to refer to the stack for
cfn-hup etc, otherwise the stack lookup by name will fail - using
the AWS::StackId parameter means we'll refer to the stack via the
full ARN and the CFN API will be able to lookup the nested stack.

ref bug 1131666

Change-Id: Ieac738df766ae1f1039e743d465cd080b2090473
Merge "heat engine : loadbalancer resource template, refer to StackId"