LU-12853 ptlrpc: zero session enviroment

LU-12853 ptlrpc: zero session enviroment

handle_recovery_req() set le_ses for request processing,
and doesn't zero it after. This leads to accessing freed memory
at keys_fill() later.

The patch also adds a cleanup for xxx_env_info, makes them equal
and combines to a single function.

Cray-bug-id: LUS-7676
Signed-off-by: Alexander Boyko <c17825@cray.com>
Change-Id: Ifad95c1177258b6f71effe5fa815f68c8426c516
Reviewed-on: https://review.whamcloud.com/36443
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Zarochentsev <c17826@cray.com>
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andrew Perepechko <c17827@cray.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Sergey Cheremencev <c17829@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>