LU-17668 ptlrpc: create env in few more threads

LU-17668 ptlrpc: create env in few more threads

like evict thread, pinger, mount process.  This avoids cases
where there is no lu_env found for a thread:

  mdt_dom_lvbo_update()) ASSERTION( env ) failed

yet another case is when MDT destroys exports - we don't need to
re-allocate a new env (including thread infos for every layer) for
each export being destroyed.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Iff7b757ad34063a3596a34998489cc3c635a02d2
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54642
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>