btrfs-progs: tests: Use --no-same-owner option for tar

btrfs-progs: tests: Use --no-same-owner option for tar

Some test failed in my nfs dir:
  ...
    [TEST]   006-bad-root-items
  tar: test.img: Cannot change ownership to uid 1000, gid 1000: Invalid argument
  tar: Exiting with failure status due to previous errors
  failed to extract default_case.tar.xz
  test failed for case 006-bad-root-items

It is because the image file's owner is:
 # tar tvf default_case.tar.xz
 -rw-r--r-- fdmanana/fdmanana 2147483648 2014-10-17 17:59 test.img

And make tar failed in chown in nfs.

It is not a big issue because we don't use nfs commonly, but extract
the image file with ownership of current user will be a better choice.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>