Few issues with Container create validation

[skobyda]

Copied from @garrett 's comment at https://github.com/cockpit-project/cockpit-podman/pull/1354#pullrequestreview-1684292014

1. Trash can icon is misaligned when there are elements pushing it vertically.

But this can be handled in a follow-up.

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2. I get an error of file not found in the autocomplete widget, but not as a message. Is this intended?