LU-3321 clio: collapse layer of cl_page

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>