Make LocalIP public function so Podman can use it

[rhatdan]

[NO NEW TESTS NEEDED]

Needed for containers/podman#12375

Signed-off-by: Daniel J Walsh [email protected]

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/kind api-change
/kind bug
/kind cleanup
/kind deprecation
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake
/kind other

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[openshift-ci]

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[rhatdan]

@mheon @Luap99 PTAL

[mheon]

Maybe go a step further and throw this into c/common?

[rhatdan]

I was thinking of that, but right now containers/common does not have a util pkg. It does have a pkg/defaultnet, which does not seem appropriate. Theoretically we could change it to pkg/net, and then move a bunch of these over.
Anyways the container_internal_linux.go is currently using buildah/util, so it made sense to put the code here.

[Luap99]

LGTM

[vrothberg]

LGTM

[vrothberg]

/lgtm

[flouthoc]

LGTM, for the record.