Fix intermittent test failures in schedule timer tests.
Fix intermittent test failures in schedule timer tests.

CenturyLinkCloud/kafka-net,gigya/KafkaNetClient,aNutForAJarOfTuna/kafka-net,BDeus/KafkaNetClient,PKRoma/kafka-net,nightkid1027/kafka-net,bridgewell/kafka-net,geffzhang/kafka-net,Jroland/kafka-net,EranOfer/KafkaNetClient,martijnhoekstra/kafka-net