Check if prefixes exist. Fix tests to work on MacOSX
Check if prefixes exist. Fix tests to work on MacOSX

dleehr/cwltool,chapmanb/cwltool,SciDAP/cwltool,dleehr/cwltool,jeremiahsavage/cwltool,SciDAP/cwltool,SciDAP/cwltool,chapmanb/cwltool,chapmanb/cwltool,SciDAP/cwltool,dleehr/cwltool,jeremiahsavage/cwltool,common-workflow-language/cwltool,dleehr/cwltool,chapmanb/cwltool,common-workflow-language/cwltool,jeremiahsavage/cwltool,common-workflow-language/cwltool,jeremiahsavage/cwltool