LU-7782 osp: save env for update callback

LU-7782 osp: save env for update callback

Because the ptlrpc_queue_wait might reset
the env to NULL, let's save the current
environment for update callback of
synchronous request.

Signed-off-by: Di Wang <di.wang@intel.com>
Change-Id: I16f0be1d1e44b5dec3253c4a0dc55af398f49de5
Reviewed-on: http://review.whamcloud.com/18493
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>