xfs: don't set XFS_BTCUR_BPRV_WASDEL in xfs_bunmapi

The XFS_BTCUR_BPRV_WASDEL flag is supposed to indicate that we are
converting a delayed allocation to a real one, which isn't the case
in xfs_bunmapi.  Setting it could theoretically lead to misaccounting
here, but it's unlikely that we ever hit it in practice.

Signed-off-by: Christoph Hellwig <hch@lst.de>
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>