add hostname to /etc/hosts when running with host network

[Luap99]

What type of PR is this?

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

What this PR does / why we need it:

Some tools depend on the hostname being present in /etc/hosts. I would
argue they are broken but its not like we can do anything about that.

This adds the hostname with the local host ip when the host network is
used. For private networking we already add the hostname.

We also now correctly force host networking in chroot mode, it was
silently ignored before thus causing extra confusion here.

How to verify it

Which issue(s) this PR fixes:

Fixes #4446

Special notes for your reviewer:

Does this PR introduce a user-facing change?

buildah now adds the hostname to /etc/hosts when running with host networking.

[TomSweeneyRedHat]

A test blipped not being able to see google.com, I've restarted.

[Luap99]

Tests are failing because of the return error with chroot and --network change, looks like a lot of tests are testing functionality that never worked.
Given how many test fails and that commit d6b43c3 can be considered a breaking change even when it never did what the users asked for I think it is just best to drop that commit and document it better. Basically every container in container workload that uses BUILDAH_ISOLATION=chroot would start blowing up when they have --network set and it is not set to host.
@TomSweeneyRedHat @flouthoc @nalind @rhatdan WDYT?

[nalind]

host should always have been the default for chroot. LGTM.

[TomSweeneyRedHat]

Backing out d6b43c3 sounds like a good plan to me @Luap99

[rhatdan]

/approve
/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Luap99, rhatdan

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[rhatdan]

/hold cancel

[SaurabhAhuja1983]

@Luap99 Thank You for working on it.
I really appreciate it.
I see there are couple of things failing in main after this merge.
Once that's done, can you please release the new version of buildah, so that i can pick it up instead of using main.

[Luap99]

A new release will be cut in the next few weeks.