Do not ask to select from list with single element
Do not ask to select from list with single element

A consequence of observations on the simplified hello.cwl and https://github.com/common-workflow-language/workflows/pull/60 .
dleehr/cwltool,chapmanb/cwltool,chapmanb/cwltool,chapmanb/cwltool,SciDAP/cwltool,chapmanb/cwltool,jeremiahsavage/cwltool,SciDAP/cwltool,common-workflow-language/cwltool,dleehr/cwltool,jeremiahsavage/cwltool,common-workflow-language/cwltool,dleehr/cwltool,SciDAP/cwltool,dleehr/cwltool,jeremiahsavage/cwltool,SciDAP/cwltool,common-workflow-language/cwltool,jeremiahsavage/cwltool