Automatic merge from submit-queue

Fix killing child sudo process in e2e_node tests

Fixes #29211.

The context is we are trying to kill a process started as `sudo kube-apiserver`, but `sudo` ignores signals from the same process group. Applying `Setpgid` means the `sudo kill` process won't be in the same process group, so will not fall foul of this nifty feature.

I also took the liberty of removing some code setting `Pdeathsig` because it claims to be doing something  in the same area, but actually it doesn't do that at all.  The setting is applied to the forked process, i.e. `sudo`, and it means the `sudo` will get killed if we (`e2e_node.test`) die.  This (a) isn't what the comment says and (b) doesn't help because sending SIGKILL to the sudo process leaves sudo's child alive.

I didn't use the "hack for linux-only" approach because I think `Setpgid` is available on all platforms that `e2e_node` builds on.