LU-2173 lod: QoS code to give up if no good OSP found

LU-2173 lod: QoS code to give up if no good OSP found

on any iteration. this code was removed by mistake in
commit 03b988a (LU-2093).

Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Change-Id: Ifa0d3a5ceeaaf84d3ec49e39bd2f337414a216ce
Reviewed-on: http://review.whamcloud.com/4300
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: Oleg Drokin <green@whamcloud.com>