xfs: set AGI buffer type in xlog_recover_clear_agi_bucket

xlog_recover_clear_agi_bucket didn't set the
type to XFS_BLFT_AGI_BUF, so we got a warning during log
replay (or an ASSERT on a debug build).

    XFS (md0): Unknown buffer type 0!
    XFS (md0): _xfs_buf_ioapply: no ops on block 0xaea8802/0x1

Fix this, as was done in f19b872b for 2 other locations
with the same problem.

cc: <stable@vger.kernel.org> # 3.10 to current
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_log_recover.c

@@ -4929,6 +4929,7 @@ xlog_recover_clear_agi_bucket(
 	agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
 	offset = offsetof(xfs_agi_t, agi_unlinked) +
 		 (sizeof(xfs_agino_t) * bucket);
+	xfs_trans_buf_set_type(tp, agibp, XFS_BLFT_AGI_BUF);
 	xfs_trans_log_buf(tp, agibp, offset,
 			  (offset + sizeof(xfs_agino_t) - 1));