This better tests the SEEK_HOLE logic which
replaced the original fiemap hole identification logic.
Also it avoids a false failure in sparse-2.sh
on reflink supporting file systems, where we
try to correlate the file sizes produced by cp and dd.
* tests/cp/sparse-2.sh: s/cp/cp --reflink=never/
* tests/cp/sparse-extents-2.sh: Likewise.
* tests/cp/sparse-extents.sh: Likewise.
* tests/cp/sparse-perf.sh: Likewise.
* tests/cp/sparse.sh: Likewise.
Fixes https://github.com/coreutils/coreutils/issues/54