LU-17173 gss: user keys go to user keyring

LU-17173 gss: user keys go to user keyring

Keys for root, that are used for Lustre internal processing, are
stored in the session keyring. That way they can be found by all
Lustre processes in userspace and in the kernel.
For end user keys, it is better to store them in the user keyring.
This simplifies key management, makes them shared accross all user
sessions, and avoids unfortunate key leak if lfs flushctx is not
called at user logout.

Test-Parameters: kerberos=true testlist=sanity-krb5
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ibb3d326e89dcacc89e77eca76cdb773861d3a8a7
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52771
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>