vfs_default: use copy_file_range()

vfs_default: use copy_file_range()

Original file on an XFS filesystem:

  $ ls -l /mnt/test/1048578-file
  -rw-rw-r--. 1 slow slow 1048578 Jun 25 11:40 /mnt/test/1048578-file

  $ xfs_bmap /mnt/test/1048578-file
  /mnt/test/1048578-file:
          0: [0..2055]: 192..2247

Copy created with cp --reflink=never:

  $ xfs_bmap /mnt/test/1048578-file-reflink-never
  /mnt/test/1048578-file-reflink-never:
          0: [0..2055]: 2248..4303

Copy created with cp --reflink=always

  $ xfs_bmap /mnt/test/1048578-file-reflink-always
  /mnt/test/1048578-file-reflink-always:
          0: [0..2055]: 192..2247

Copy done from a Windows client:

  $ xfs_bmap /mnt/test/1048578-file\ -\ Copy
  /mnt/test/1048578-file - Copy:
          0: [0..2055]: 192..2247

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12033

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Jun 30 17:40:23 UTC 2021 on sn-devel-184