Fix setOldestVersion

We were not accumulating keyUpdates strictly faster than we were
spending them for a monotonically increasing workload.

ConflictSet.cpp

@@ -1851,11 +1851,11 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
       auto begin = std::span<const uint8_t>(w.begin.p, w.begin.len);
       auto end = std::span<const uint8_t>(w.end.p, w.end.len);
       if (w.end.len > 0) {
-        keyUpdates += 2;
+        keyUpdates += 3;
         addWriteRange(root, oldestVersion, begin, end, w.writeVersion,
                       &allocators, this);
       } else {
-        keyUpdates += 1;
+        keyUpdates += 2;
         addPointWrite(root, oldestVersion, begin, w.writeVersion, &allocators,
                       this);
       }
@@ -1870,7 +1870,7 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     Node *prev = firstGeq(root, removalKey).n;
     // There's no way to erase removalKey without introducing a key after it
     assert(prev != nullptr);
-    while (keyUpdates-- > 0) {
+    for (; keyUpdates > 0; --keyUpdates) {
       Node *n = nextLogical(prev);
       if (n == nullptr) {
         removalKey = {};