Fix setOldestVersion bug

We should update the oldest version even if we don't have enough
keyUpdates to do

ConflictSet.cpp

@@ -1863,10 +1863,13 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   }
 
   void setOldestVersion(int64_t oldestVersion) {
-    if (oldestVersion <= this->oldestVersion || keyUpdates < 1000) {
+    if (oldestVersion <= this->oldestVersion) {
       return;
     }
     this->oldestVersion = oldestVersion;
+    if (keyUpdates < 1000) {
+      return;
+    }
     Node *prev = firstGeq(root, removalKey).n;
     // There's no way to erase removalKey without introducing a key after it
     assert(prev != nullptr);