LU-12034 obdclass: put all service's env on the list

LU-12034 obdclass: put all service's env on the list

to be able to lookup by current thread where it's too
complicated to pass env by argument.

this version has stats to see slow/fast lookups. so, in sanity-benchmark
there were 172850 fast lookups (from per-cpu cache) and 27228 slow lookups
(from rhashtable). going to see the ration in autotest's reports.

Fixes: 2339e1b3b690 ("LU-11483 ldlm ofd_lvbo_init() and mdt_lvbo_fill() create env")
Fixes: e02cb40761ff ("LU-11164 ldlm: pass env to lvbo methods")

Change-Id: Ia760e10fa5c68e7a18284e4726d215b330fc0eed
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34566
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andrew Perepechko <c17827@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>