stack-update from a non-HOT stack to a HOT stack fails

[Robert Collins]

This is using the tripleo overcloud stack - deploy a version prior to our HOT merges, then update :

| stack_status_reason | StackValidationFailed: Property error : NovaCompute6: |
| | key_name Value must be a string

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/113739

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/113739
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=afd538664f5041df1070e5e8b42b5bab979dc9f7
Submitter: Jenkins
Branch: master

commit afd538664f5041df1070e5e8b42b5bab979dc9f7
Author: Steve Baker <email address hidden>
Date: Wed Aug 13 13:29:42 2014 +1200

    Use new template for resource update reparse

    If the stack-update is switching from pre-HOT to HOT then
    the update will fail because the functions are resolved
    using the pre-HOT template.

    This change uses the new template for the reparse instead of the
    old one. It fixes the issue observed but any other effects are
    unknown.

    Change-Id: I2f749375ccd7ca917387ef96856b1fc248c8567b
    Closes-Bug: #1356097