fix(fleetshard): use FQDN for k8s svc

[stehessel]

Description

Use the FQDN to prevent unnecessary DNS lookups and to make sure that the no_proxy env var is set correctly with protocol prefix.

Checklist (Definition of Done)

• Unit and integration tests added
• Added test description under Test manual
• Documentation added if necessary (i.e. changes to dev setup, test execution, ...)
• CI and all relevant tests are passing
• Add the ticket number to the PR title if available, i.e. ROX-12345: ...
• Discussed security and business related topics privately. Will move any security and business related topics that arise to private communication channel.
• Add secret to app-interface Vault or Secrets Manager if necessary
• RDS changes were e2e tested manually
• Check AWS limits are reasonable for changes provisioning new resources

Test manual

Tested on OpenShift cluster.

[stehessel]

/retest

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ivan-degtiarenko, stehessel

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