LU-12578 obdecho: reuse an cl env cache for obdecho survey

LU-12578 obdecho: reuse an cl env cache for obdecho survey

obdecho enviroment is already CL_thread type, so
easy to reuse cl_env cache instead of allocate env on each
ioctl call. It reduce cpu usage dramatically.

Cray-bug-id: LUS-7552
Signed-off-by: Alexey Lyashkov <c17817@cray.com>
Change-Id: Id4b36626233be6b65efc4daef649bf0ef97c2e60
Reviewed-on: https://review.whamcloud.com/35700
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>