LU-4488 build: fix compilation with --enable-invariants

LU-4488 build: fix compilation with --enable-invariants

Fix the build which was broken since the following commit:

    commit 0a259bd7dbac76d75b89a389bc317720153aa452
    Author: Jinshan Xiong <jinshan.xiong@intel.com>
    Date:   Mon Sep 30 15:00:38 2013 -0700

    LU-3321 clio: collapse layer of cl_page

    Move radix tree to osc layer to for performance improvement.

    Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
    Change-Id: I93e3cb8352f7be41c23465b12945874316aa1809
    Reviewed-on: http://review.whamcloud.com/7892
    Tested-by: Jenkins
    Tested-by: Maloo <hpdd-maloo@intel.com>
    Reviewed-by: Lai Siyao <lai.siyao@intel.com>
    Reviewed-by: Bobi Jam <bobijam@gmail.com>
    Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: Ie8543513852d98d0aa82bca0f227d286cdf8ebd2
Reviewed-on: http://review.whamcloud.com/8853
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>