fix sproadic failure in UT WhenMaxSizeIsReachedThenEnqueuedTranmissionsAreDropped
fix sproadic failure in UT WhenMaxSizeIsReachedThenEnqueuedTranmissionsAreDropped

pharring/ApplicationInsights-dotnet,Microsoft/ApplicationInsights-dotnet,pharring/ApplicationInsights-dotnet,pharring/ApplicationInsights-dotnet