[DMN Editor] Unable to Execute model with imported nodes

This Iss was spotted during review of PR for DROOLS-3829 and DROOLS-3934.

User is not able to execute model with imported nodes.

Steps To Reproduce

1. Deploy the attached project to kie server
2. Try to execute the model as:

   curl -u testadmin:'admin1234;' -H "accept: application/json" -H "content-type: application/json" -X POST "http://localhost:8080/kie-server/services/rest/server/containers/dmn.imports/dmn" -d "{ \"model-namespace\" : \"https://github.com/kiegroup/drools/kie-dmn/_547C193C-0B52-45F5-877E-F74A7DD29838\", \"model-name\" : \"routes\", \"decision-name\" : [\"Traffic.Traffic\" ], \"decision-id\" : [ ], \"dmn-context\" : {\"cars per hour\" : 10}}"
   

3. You will get result:

   {
     "type" : "FAILURE",
     "msg" : "Error from container 'dmn.imports'Unable to locate DMN Model to evaluate",
     "result" : null
   }

4. Error appears in server log: error.log

Actual result

There is response error message and error in server log

Expected result

Model is executed