Revert "Prevent divide-by-zero for incomplete threads"

This reverts commit 9740d85d96a86414a0020338811f8d5f7049a7c5.

common/Perf/Azure.Test.Perf/PerfProgram.cs

@@ -190,10 +190,7 @@ private static async Task RunTestsAsync(IPerfTest[] tests, PerfOptions options,
             var latency = warmup ? false : options.Latency;
 
             _completedOperations = new int[options.Parallel];
-
-            // Initialize _lastCompletionTimes with non-zero values to avoid divide-by-zero for threads
-            // with no completed operations.
-            _lastCompletionTimes = Enumerable.Repeat(TimeSpan.MinValue, options.Parallel).ToArray();
+            _lastCompletionTimes = new TimeSpan[options.Parallel];
 
             if (latency)
             {