LU-911 obdapi: add env to few methods

LU-911 obdapi: add env to few methods

so that soon-coming OFD doesn't need to reallocate env on every
request. Instead OST will be passing env down as MDT does.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I605b4cdb5eb1f2984c303646c161fbde43d155ef
Reviewed-on: http://review.whamcloud.com/1847
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>