xfs/111: fix cp of missing file

xfs/111: fix cp of missing file

After installing the test suite, src directory only contains binary
programs in the final building directory. Here executing "cp src/itrash.c
$SCRATCH_MNT/${I}" will output "cp: cannot stat 'src/itrash.c': No
such file or directory" error message. Fix it.

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>