During filesystem creation with -d option files copied from given

During filesystem creation with -d option files copied from given
directory. If supported, FS_IOC_FIEMAP ioctl is used to get file
extents. For empty file fm_mapped_extents is 0 and no error code
is returned, because this is not fail situation.

Without this patch errno from previous operation is returned and
successful FS_IOC_FIEMAP ioctl call for empty file is interpreted
as error.

Signed-off-by: Artem Blagodarenko <artem.blagodarenko@seagate.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>