fix: [multi-slb] Put the service in the load balancer that has no lab…

[nilo19]

…el/namespace selector only if there is no other choice for the service.

What type of PR is this?

/kind bug

What this PR does / why we need it:

For a load balancer with no label/namespace selectors:
current behavior: it can be a placement targets for services.
new behavior: it can be a placement target for a service if and only if there is no other choice for the service.
Ref: #5261

Which issue(s) this PR fixes:

Fixes #5261

Special notes for your reviewer:

Does this PR introduce a user-facing change?

fix: [multi-slb] Put the service in the load balancer that has no label/namespace selector only if there is no other choice for the service.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[feiskyer]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: feiskyer, nilo19

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