LU-17612 gss: always try to unlink key in error

LU-17612 gss: always try to unlink key in error

In case of error in context negotiation carried out in userspace,
always try to unlink key to avoid leaking it.

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: Ic771f1e4f1b6474caaa89f63c3b02678e163d3d3
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54316
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>