Enhance flaky test TestRemoveUserCbHandlerOnPathRemoval

[kaisun2000]

Issues

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Fixes #1102
TestRemoveUserCbHandlerOnPathRemoval has a flaky test

Description

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Assert .assertEquals(watchPaths.get("existWatches").size(), 2, "Should have 2 exist-watches: CURRENTSTATE/{oldSessionId} and CURRENTSTATE/{oldSessionId}/TestDB0");
is flaky.

Tests

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This test case pass. This pull only touch test case logic.

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Code Quality

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[jiajunwang]

LGTM

[kaisun2000]

This PR is ready to be merged, approved by @jiajunwang

Fix flaky test testRemoveUserCbHandlerOnPathRemoval # #1102

TestRemoveUserCbHandlerOnPathRemoval has a flaky assert. Addres
the assertion in this diff.