revert erroneous changes in cwltool/sandbox.py
revert erroneous changes in cwltool/sandbox.py

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