JFS: make special inodes play nicely with page balancing

This patch fixes up a few problems with jfs's reserved inodes.

1. There is no need for the jfs code setting the I_DIRTY bits in i_state.
   I am ashamed that the code ever did this, and surprised it hasn't been
   noticed until now.

2. Make sure special inodes are on an inode hash list.  If the inodes are
   unhashed, __mark_inode_dirty will fail to put the inode on the
   superblock's dirty list, and the data will not be flushed under memory
   pressure.

3. Force writing journal data to disk when metapage_writepage is unable to
   write a metadata page due to pending journal I/O.

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>