LU-5126 libcfs: fix illegal page access of tracefiled()

LU-5126 libcfs: fix illegal page access of tracefiled()

After failure happens and put_pages_back() returns the pages,
tracefiled() should not go on itering on the page list.
Otherwise, some pages might be accessed illegally.

Signed-off-by: Li Xi <lixi@ddn.com>
Change-Id: I34dd91e3a7ca7d49e67c2bd587c481eb71873003
Reviewed-on: http://review.whamcloud.com/10524
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>