Description of problem:
Getting an error when referencing external files

Version-Release number of selected component (if applicable):
5.7

How reproducible:
always

Steps to Reproduce:
1. Create an Orchestration template that references external files:

heat_template_version: newton

resources:
  a_file:
    type: https://pastebin.com/raw/hVbif6z9
 # the linked resource references get_file: https://www.google.com/robots.txt


Actual results:
Heat complains about get_file: https://www.google.com/robots.txt not in the files dict
getting the files dict from heat, the file is not there
openstack stack files list mystack
...
NO https://www.google.com/robots.txt around

Expected results:
the stack to be created

Additional info:
https://github.com/ManageIQ/manageiq/issues/15563