fix(transparent-proxy): make iptables mode detection more defensive (backport of #9776)

[kumahq]

Automatic cherry-pick of #9776 for branch release-2.5

Generated by action

cherry-picked commit fdebf4b
⚠️ ⚠️ ⚠️ Conflicts happened when cherry-picking! ⚠️ ⚠️ ⚠️

On branch release-2.5
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Changes to be committed:
	modified:   pkg/transparentproxy/config/config.go
	modified:   pkg/transparentproxy/iptables/builder/builder_restore.go
	modified:   pkg/transparentproxy/iptables/builder/builder_table_raw.go
	modified:   pkg/transparentproxy/iptables/setup.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   pkg/transparentproxy/iptables/builder/builder.go