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.

Lustre-change: https://review.whamcloud.com/54316
Lustre-commit: 21aa8404a42b79f7e0434cfe75411f85d7ee063a

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-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54557
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>