xfs: Simplify xfs_attr_node_addname

xfs: Simplify xfs_attr_node_addname

Source kernel commit: bf4a5cfffee096624764d5aed82f786c708dfe90

Invert the rename logic in xfs_attr_node_addname to simplify the
delayed attr logic later.

Signed-off-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>