ocfs2: fix rename vs unlink race

If another node unlinks the destination while ocfs2_rename() is waiting on a
cluster lock, ocfs2_rename() simply logs an error and continues. This causes
a crash because the renaming node is now trying to delete a non-existent
inode. The correct solution is to return -ENOENT.

Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>