Avoid parse already parsed Workflows
Avoid parse already parsed Workflows

When cwltool tries to update a workflow that includes more than once the
same subworkflow an exception is raised. This is a product of the updating
procedure where workflows are passed by reference in the document. Once
a workflow has been updated, it should not be processed again.

dleehr/cwltool,common-workflow-language/cwltool,common-workflow-language/cwltool,common-workflow-language/cwltool,dleehr/cwltool,dleehr/cwltool,dleehr/cwltool