Workflows with v1.0 tag produce error with tools with v1.1 tag.

## Expected Behavior
Cwl tool validates with some warnings about inputs.

## Actual Behavior
Workflows written in v1.0 produce an error indicating a specification is not found in tools wrapped with v1.1

## Workflow Code
```
Workflow

#!/usr/bin/env cwl-runner
cwlVersion: v1.0
class: Workflow
label: Symphony post-processing workflow.

requirements:
InlineJavascriptRequirement: {}
MultipleInputFeatureRequirement: {}
StepInputExpressionRequirement: {}
SubworkflowFeatureRequirement: {}

inputs:
ForwardReads: File
ReverseReads: File
Reference: File
MaxThreads: int
SampleID: string
KnownSiteVCF: File
AnnotationDB: Directory

Tool

cwlVersion: v1.1
class: CommandLineTool

$namespaces:
arv: "http://arvados.org/cwl#"
cwltool: "http://commonwl.org/cwltool#"

hints:
arv:APIRequirement: {}

requirements:
DockerRequirement:
dockerPull: "broadinstitute/gatk:4.1.7.0"
InlineJavascriptRequirement: {}
NetworkAccess:
networkAccess: true
ResourceRequirement:
ramMin: 40000 # [MB]
coresMin: 4 # [cores]
tmpdirMin: 10000 # [MB]

```

## Full Traceback
```pytb
ERROR Tool definition failed validation:
../Tools/GATK/GATK-GenomicsDBImport.cwl:2:1: Field `cwlVersion` contains undefined reference to
`file:///Users/djevanclark/Documents/Sinai/covid/biocwl/Tools/GATK/v1.1
```

## Your Environment
* cwltool version: 3.0.20200324120055