test: Simplify pam_sss_gss setup in check-system-s4u-ssh
test: Simplify pam_sss_gss setup in check-system-s4u-ssh

Don't rewrite the whole sudo PAM file, just insert pam_sss_gss.so as the
manpage suggests.

Also adjust the comment: The sudo part does *not* currently test the
forwarded S4U ticket, as ssh does not do any kind of forwarding. This
initializes a fresh TGT.

martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit