Description of problem:
Can't order service via api when the service dialog values are passed, fails with below error

{"error":{"kind":"bad_request","message":"Failed to order Service Template id:39 name:'niroy-test' - Basic Information/Extra Variables/var1 is required","klass":"Api::BadRequestError"}}

Version-Release number of selected component (if applicable):
5.9.5.3

How reproducible:
Always

Steps to Reproduce:
1. Create a service dialog with 2 text boxes 
2. Create a catalog item using that service dialog
3. take a note of the catalog and catalog item ID
4. Run below query to order the service (pass the values)

curl -k -u admin:smartvm -X POST -H "Accept:application/json" -d '{ "action" : "order", "href" : "https://<IP>/api/service_templates/39", "param_var1" : "hello", "param_var2" : "test" }' https://<IP>/api/service_catalogs/1/service_templates


Actual results:
Service order fails

{"error":{"kind":"bad_request","message":"Failed to order Service Template id:39 name:'niroy-test' - Basic Information/Extra Variables/var1 is required","klass":"Api::BadRequestError"}}

Expected results:
Service order should succeed

Additional info:
This is regression, works fine in 5.9.4.7