NTFS: Modify fs/ntfs/mft.c::write_mft_record_nolock() and

NTFS: Modify fs/ntfs/mft.c::write_mft_record_nolock() and
      fs/ntfs/aops.c::ntfs_write_mst_block() to only check the dirty state
      of the first buffer in a record and to take this as the ntfs record
      dirty state.  We cannot look at the dirty state for subsequent
      buffers because we might be racing with
      fs/ntfs/aops.c::mark_ntfs_record_dirty().

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>