LU-2899 lod: get ldo_stripenr correctly

LU-2899 lod: get ldo_stripenr correctly

Current code relies on lod_statfs_and_check() to count the number of
activated LOD targets, while lod::ldo_stripenr derivation happens
before calling lod_statfs_and_check(), and that makes
lod::ldo_stripenr not accurate.

This patch make sure lod_statfs_and_check() called before updating
::ldo_stripenr. And if there is [de]activation happens on OST target,
client needs wait 2*lod_qos_maxage seconds to get accurate
ld_active_tgt_count number.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: I37bebc69f876dd68da609fb5180bc6db36f01e84
Reviewed-on: http://review.whamcloud.com/5573
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>