staging: lustre: LNet drop rule implementation

staging: lustre: LNet drop rule implementation

This is implementation of LNet Drop Rule, which can randomly drop
LNet messages at specified rate.

LNet Drop Rule can only be applied to receive side of message. User
can add drop_rule either on end point of cluster (client/server) or
on LNet routers.

Here are lctl command to control LNet Drop Rules:
 - net_drop_add -s SRC_NID -d DEST_NID --rate VALUE
   drop 1/@VALUE of messages from @SRC_NID to @DEST_NID

 - net_drop_del -s SRC_NID -d DEST_NID
   remove all drop rules from @SRC_NID to @DEST_NID

 - net_drop_list
   list all drop rules on current node

 Examples:
 - lctl net_drop_add -s *@o2ib0 -d 192.168.1.102@tcp 1000
   add new drop rule, it will drop 1/1000 messages from network o2ib0
   to 192.168.1.102@tcp

 - lctl net_drop_add -s 10.8.6.123@o2ib1 -d * 500
   add new drop rule, it will drop 1/500 messages from 10.8.6.123@o2ib1
   to all nodes

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5435
Reviewed-on: http://review.whamcloud.com/11314
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>