Description of problem:
A stack creation in Openstack dashboard fail because "boot_source" is not known as a property.

Version-Release number of selected component (if applicable):
Openstack 16.2, 17.1

How reproducible:
Always

Steps to Reproduce:
1. In Horizon create an example template with a volume with image associated to be launched in a stack.
2. Check the template generated.
2. Try to create the stack.

Actual results:
Pop-up error message.

Expected results:
Stack created successfully.

Additional info:

Workaround:
Manually change the YAML file of the stack as below because what cause the issue is the parameter boot_source that is not valid.
From:
properties:
name: test
size: 10
volume_type: "0000000-bf56-42df-0000-ab2a85cc7998"
availability_zone: dc1
boot_source: image
image: "0000000-5780-4b19-0000-972f540c2279"
To:
properties:
name: test
size: 10
volume_type: "0000000-bf56-42df-0000-ab2a85cc7998"
availability_zone: dc1
image: "0000000-5780-4b19-0000-972f540c2279"