xfs: fix xfs_quiesce_data

We need to do a synchronous xfs_sync_fsdata to make sure the superblock
actually is on disk when we return.

Also remove SYNC_BDFLUSH flag to xfs_sync_inodes because that particular
flag is never checked.

Move xfs_filestream_flush call later to only release inodes after they
have been written out.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Alex Elder <aelder@sgi.com>