Refactor stsSetupHostAliases for conditional host aliases

[HighWatersDev]

This PR is meant to fix an issue with Gatekeeper denying the request due to host aliases being passed, even though it's an empty list.

E1007 1932.297598 1 statefulset-reconciler.go:364] doCreateStatefulSet():Host:0-0[0/0]:example/example-clickhouse:StatefulSet create failed. err: admission webhook "validation.gatekeeper.sh" denied the request: [podsecurity] Pods cannot specify host aliases

Thanks for taking the time to contribute to clickhouse-operator!

Please, read carefully instructions on how to make a Pull Request.

This will help a lot for maintainers to adopt your Pull Request.

Important items to consider before making a Pull Request

Please check items PR complies to:

• All commits in the PR are squashed. More info
• The PR is made into dedicated next-release branch, not into master branch¹. More info
• The PR is signed. More info

--

¹ If you feel your PR does not affect any Go-code or any testable functionality (for example, PR contains docs only or supplementary materials), PR can be made into master branch, but it has to be confirmed by project's maintainer.

[HighWatersDev]

@sunsingerus anything I can help clarify with this PR? I see waiting reply label