Set a flag in the inode if we have stored the objid there, so we know when

Set a flag in the inode if we have stored the objid there, so we know when
we should clear it.   Also make clear_inode() the default cl_delete_inode
method so we don't have to do an extra check for it.

In the end, I think that the objid issue is not a source of any problems,
because ext3_delete() will only call ext3_truncate() if i_blocks is non-zero,
and it isn't (this is why we weren't seeing any errors from ext3 trying to
truncate "blocks" that are not allocated).