The next step in divorcing metadata I/O management from struct inode is
to pass struct ocfs2_caching_info to the journal functions.  Thus the
journal locks a metadata cache with the cache io_lock function.  It also
can compare ci_last_trans and ci_created_trans directly.

This is a large patch because of all the places we change
ocfs2_journal_access..(handle, inode, ...) to
ocfs2_journal_access..(handle, INODE_CACHE(inode), ...).

Signed-off-by: Joel Becker <joel.becker@oracle.com>