generic/486: Get rid of the redundant error=%d printing

generic/486: Get rid of the redundant error=%d printing

1) Without the fix, perror() can indicate the actual error(ENODATA).
2) After calling perror() and redirecting the output of perror()
   to a file, errno seems to be set to EINVAL unexpectedly.
   See the following mail for detailed info:
   https://www.spinics.net/lists/fstests/msg09675.html

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>