Fix bounded consistent hash with filtered endpoints

[shrikant23codes]

Fix boundedLoadSearch so it advances to the next hash ring entry when the current endpoint has been filtered out. Filtered endpoints can happen before load balancing, for example through fade-in.

In bounded-load mode, the algorithm starts from the normal consistent-hash target. If that endpoint is overloaded, it walks forward in the hash ring looking for another endpoint below the load threshold.

Before this change, if the walk reached a filtered endpoint, the loop continued without advancing the ring index. This could repeatedly check the same filtered endpoint and eventually return it.

Example case:

Route endpoints: [A, B, C]
Candidate endpoints: [A, C]    // B was filtered out

Hash ring walk:  A -> B -> C

- A is selected by consistent hash but is overloaded.
- The algorithm moves to B.
- B is not in the candidate list, so it should be skipped.
- Previously the ring index was not advanced when skipping B.

With this change, the algorithm advances to C.

Tests

go test ./loadbalancer -run TestConsistentHashBoundedLoadSearchSkipsFilteredEndpoints
go test ./loadbalancer

Suggested label: bug
Fixes: #4139

[MustafaSaber]

Thanks, nice catch!