Fix fsl_sub issues
A previous change allowing specification of the correct FSLSUB_CONF file to use was mistakenly trying to subscript a NoneType object. Update run_template_construction.py to use the non-deprecated version of func_to_cmd.
A previous change allowing specification of the correct FSLSUB_CONF file to use was mistakenly trying to subscript a NoneType object. Update run_template_construction.py to use the non-deprecated version of func_to_cmd.