LU-2133 lnet: wrong peer state reported

When peer health support is disabled, peer state as shown in
/proc/sys/lnet/peers and by IOC_LIBCFS_DEBUG_PEER should be "NA".
Otherwise wrong states could be shown because the peer aliveness time
stamps are not refreshed when peer health is disabled.

Signed-off-by: Isaac Huang <he.huang@intel.com>
Change-Id: Ice5c6651ca5d2620495a0c37de9a22aebd644d0a
Reviewed-on: http://review.whamcloud.com/5955
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>