Fix test 128 to work when sh is not the fsgqa login shell.

Merge of master-melb:xfs-cmds:26837a by kenmcd.

128

@@ -45,11 +45,11 @@ cp `which ls` $SCRATCH_MNT
 chmod 700 $SCRATCH_MNT/nosuid
 chmod 4755 $SCRATCH_MNT/ls
 
-su - $qa_user -c "$SCRATCH_MNT/ls $SCRATCH_MNT/nosuid >/dev/null 2>&1"
+su -s/bin/sh - $qa_user -c "$SCRATCH_MNT/ls $SCRATCH_MNT/nosuid >/dev/null 2>&1"
 if [ $? -eq 0 ] ; then
 	echo "Error: we shouldn't be able to ls the directory"
 fi
 umount $SCRATCH_DEV
 
 status=0
-exit 
+exit