Add integration tests

The [**workflow-service**](https://github.com/common-workflow-language/workflow-service) repo has some nice, relatively lightweight [integration tests](https://github.com/common-workflow-language/workflow-service/blob/master/test/test_integration.py) for their WES server/client. Could adapt these and add some sort of TRS calls to test the orchestrator.

Review test/test_integration.py in the linked workflow-service repository to understand its lightweight WES server/client integration tests. Then inspect the cloud-interop-testing orchestrator entry points and determine how TRS calls should be exercised. Done means adding integration coverage that tests the orchestrator through TRS calls.

Written by the indexing model from the issue text.