🌱 e2e: log leftover processes to eventually detect zombies

[chrischdi]

What this PR does / why we need it:

Provides the output of ps -ef at the end of a test, to eventually detect existing zombie processes.

Tries to gather this data for inspecting #8560 some more.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

[killianmuldoon]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: f845341387231af7d3b74f21feb5e103dd0248fe

[sbueringer]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

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[sbueringer]

/cherry-pick release-1.4

[sbueringer]

/cherry-pick release-1.3

[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #8671

In response to this:

/cherry-pick release-1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-infra-cherrypick-robot]

@sbueringer: new pull request created: #8672

In response to this:

/cherry-pick release-1.3

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[g-gaston]

/area e2e-testing