Install heat-cfntools and heat-templates repos

These projects contain agents which can be installed on custom
images. Installing these repos will allow a future change to
build a custom image containing these projects. This will allow
gating on any changes in these projects by running heat-slow
on the custom image.
The corresponding devstack-gate change is
https://review.openstack.org/#/c/92055/
Change-Id: I7b1343c094f755f79ddeb1bac3ff4c0daa3fb70c
Merge "Install heat-cfntools and heat-templates repos"