JIRA: https://jira.spring.io/browse/INT-4167
Since the current `ZkLock.tryLock()` is based on the fact of waiting for **at most 1 second**, that still has some timing issue for test-case, when the network delay may affect our expectation.
* Add `Thread.sleep()` with `while()` to the `ZkLockRegistryTests.testTryLock()` test to spin until successful `tryLock()`
**Cherry-pick to 4.3.x & 4.2.x**
Note: to avoid cherry-pick conflict for `4.2.x` just fully copy/paste the modified test
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