interfaces.afni 3drefit was not running

removed the "-prefix outfile" part, since 3drefit works only on the inputfile itself and does not allow this option.

now it will work if you give the same out_file name as in_file name
however if you give no out filename it might not work if your
infile is a .nii or .nii.gz since afni will make briks. So still not perfect....