LU-300: Oops in cl_page_put of page fault path

LU-300: Oops in cl_page_put of page fault path

This problem is due to the unintialization of cl_io, so that an invalid page
address will be accessed in vvp_io_fault_fini().

Change-Id: Ic85a5d22e175cc74ada0e51831142d9f37798c08
Signed-off-by: Jinshan Xiong <jay@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/530
Tested-by: Hudson
Reviewed-by: wangdi <di.wang@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>