TestDeleteLog() was flaky.
TestDeleteLog() was flaky.

Due to eventual consistency.  Fix it with an Eventually().

Change-Id: I6aa0471336089b20a15b6c8ee3785b82960013df

jsimonweb/csharp-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,jsimonweb/csharp-docs-samples,jsimonweb/csharp-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,GoogleCloudPlatform/dotnet-docs-samples,jsimonweb/csharp-docs-samples