LU-2424 ptlrpc: reduce initial buffers count

LU-2424 ptlrpc: reduce initial buffers count

Separate buffers count for server and client services.
Reduce inititial allocation for client ("ldlm_cbd") because
its not required a lot. This reduced unreclaimable memory
usage after just mount from 233036kB to 97386kB.

Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: I56fcbe6c45c61ba4876bce5482169ea06a03638c
Reviewed-on: http://review.whamcloud.com/5719
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>