LU-1484 kernel: pass RHEL5 build for 2.6.18-308

For vanilla kernel, proc_dir_entry::deleted and ::pde_users co-exists
from 2.6.23 to 2.6.23.17.

For some RHEL5 kernels, it defines co-existings
proc_dir_entry::deleted and proc_dir_entry_aux::pde_users.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Ic0a381aa44708ff0545da376c1be05b13efa523f
Reviewed-on: http://review.whamcloud.com/5129
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Peng Tao <bergwolf@gmail.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>