Resource Requirement tests fail when more than one test suite is running at CI servers

```

Test dynamic resource reqs referencing inputs
Command '/var/lib/jenkins/workspace/cwltool-pr-conformance-multiver@3/version/v1.0/cwltool-venv2.7 /bin/cwltool --outdir=/tmp/tmprFFUeF --quiet v1.0/dynresreq.cwl v1.0/dynresreq-job.json'
returned non-zero exit status 1
--
  | Test simple workflow with a dynamic resource requirement
Command '/var/lib/jenkins/workspace/cwltool-pr-conformance-multiver@3/version/v1.0/cwltool-venv2.7/bin/cwltool --outdir=/tmp/tmplXjJhQ --quiet v1.0/dynresreq-workflow.cwl v1.0/dynresreq-job.json'
returned non-zero exit status 1

```

Error Message
```
Command '/var/lib/jenkins/workspace/cwltool-pr-conformance-multiver@3/version/v1.0/cwltool-venv2.7/bin/cwltool --outdir=/tmp/tmprFFUeF --quiet v1.0/dynresreq.cwl v1.0/dynresreq-job.json' returned non-zero exit status 1

Stacktrace

Command '/var/lib/jenkins/workspace/cwltool-pr-conformance-multiver@3/version/v1.0/cwltool-venv2.7/bin/cwltool --outdir=/tmp/tmprFFUeF --quiet v1.0/dynresreq.cwl v1.0/dynresreq-job.json' returned non-zero exit status 1

Standard Error

Workflow error, try again with --debug for more information:
Expression evaluation error:
inputs.special_file does not contain key 'size'
```