Nightly build gets stuck ClientExpirationListenerTest

[ihsandemir]

ClientExpirationListenerTest bothNotified_afterExpirationOfEntries test gets stuck at nightly tests:
https://hazelcast-l337.ci.cloudbees.com/view/Clients/job/cpp-linux-nightly-maintenance-32-SHARED-Debug/3/

https://hazelcast-l337.ci.cloudbees.com/job/cpp-linux-nightly-64-SHARED-Release/3/console

[ihsandemir]

PR #120 fixes the problem.