LU-17528 gss: cleanup gss api usage

LU-17528 gss: cleanup gss api usage

The lucid context support has been available from at least
krb5 1.7, and even RHEL7 ships with a more recent version.
So drop support for non-lucid api, and cleanup gss api usage.

Test-Parameters: trivial
Test-Parameters: kerberos=true testlist=sanity-krb5
Test-Parameters: testgroup=review-dne-selinux-ssk-part-2
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I91fb706d2444c199156423b57a8c1ef24a0c3420
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54063
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Bruno Faccini <bfaccini@nvidia.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>