Ensure we do not oversubscribe freespace for AIO stress test (take 2).

Merge of master-melb:xfs-cmds:21493a by kenmcd.

113

@@ -105,12 +105,12 @@ procs=20
 _check_test_fs
 
 # the default
-_do_test 1 "-I120m" $count 1
+_do_test 1 "-s 120m" $count 1
 
 # and the default with multiprocess
-_do_test 2 "-I10m" $count $procs
+_do_test 2 "-s 10m" $count $procs
 
 # as above, but now using direct IO
-_do_test 3 "-I10m -O" $count $procs
+_do_test 3 "-s 10m -O" $count $procs
 
 exit