Ladakh800bcls: fixup HwSwitchMatcher exception in AgentNeighborTest*

[sarahfu331]

Pre-submission checklist

• [√] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
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Summary

Desciption:
AgentNeighborTest* failed with following exception
C++ exception with description "HwSwitchMatcher::switchId api must be called only when there is a single switchId" thrown in the test body.

Root Cause:
On multi NPU platform, in function facebook::fboss::utility::NeighborInfo getNeighborInfo, when calling following
auto switchId = ensemble.getSw()
->getScopeResolver()
->scope(ensemble.masterLogicalPortIds())
.switchId();

scope(ensemble.masterLogicalPortIds()) returns an array, so can't get switchId().

Fix:
As this function is designed to retrieve the current state of neighbor entry for a specific interfaceId directly from the ASIC, so changed to get the switchId based on the interfaceId information.

Test Plan

rerun all tests of AgentNeighborTest1/3/5/7* and PASSED, AgentNeighborTest0/2/4/6 failed with other errors, will fix and track with other PR
log.tar.gz