LU-56 lnet: LNet message event cleanup

LU-56 lnet: LNet message event cleanup

In current version, LNet message events are assigned at many places,
it's not easy to maintain, also, assignments of some fields of event
need to be protected by lock and some don't need, this will be a
problem for upcoming LNet SMP improvements.
This patch created a new function lnet_build_msg_event(), all events
are assigned inside this function and it can be called w/o lock
protection.
This is an intermediate patch for LNet SMP improvements.

Signed-off-by: Liang Zhen <liang@whamcloud.com>
Change-Id: Ief8722a15d17909e3844149c55d24fb22ed0c04c
Reviewed-on: http://review.whamcloud.com/2983
Reviewed-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-by: Doug Oucharek <doug@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>