* tests/cp/fiemap-2: Enable the fiemap check for files, which
will enable the test for files on ext3.
* tests/cp/fiemap-perf: Comment why we're not enabling for ext3.
* tests/cp/sparse-fiemap: Ditto. Also sync the files before
doing a fiemap which was needed for ext4 loop back at least.
Add a comment that FIEMAP_FLAG_SYNC is ineffective, thus
requiring the explicit syncs.
* tests/fiemap-capable: A new python script to determine
if a specified path supports fiemap.
* tests/init.cfg (fiemap_capable_): Use the new python script.
* tests/Makefile.am (EXTRA_DIST): Include the new python script.
