LU-56 lnet: cleanup for rtrpool and LNet counter

LU-56 lnet: cleanup for rtrpool and LNet counter

This patch covered a few of things:
- code cleanup for router buffer pools
- code cleanup for error handling in lnet_prepare()
- code cleanup for LNet counters

This is an intermediate patch for LNet SMP improvements.

Signed-off-by: Liang Zhen <liang@whamcloud.com>
Change-Id: I554d6acb79a55dd77f709d3b6633f157f50a8cee
Reviewed-on: http://review.whamcloud.com/3091
Reviewed-by: Doug Oucharek <doug@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>