Drain all pending work in hashtable's setOldestVersion

Bench.cpp

@@ -60,7 +60,6 @@ void benchConflictSet() {
   ConflictSet cs{0};
 
   bench.batch(kOpsPerTx);
-  bench.minEpochIterations(10000);
 
   int64_t version = 0;
 
@@ -239,6 +238,8 @@ void benchConflictSet() {
 
   cs.setOldestVersion(version - kMvccWindow);
 
+  bench.minEpochIterations(1000000);
+
   {
     bench.run("monotonic increasing point writes", [&]() {
       auto v = ++version;