@Override
    protected void afterDefragmentationCountFetched() {
      if (firstDefragmentation) {
        firstDefragmentation = false;
        // Force defragmentation into thinking a concurrent defragmentation happened.
        defragmentationCount.incrementAndGet();
      } else {
        super.afterDefragmentationCountFetched();
      }
    }
Just like Fragment except that the first time allocate is called it returns false indicating
that the allocate failed. In a real system this would only happen if a concurrent allocate
happened. This allows better code coverage.
geode-core/src/test/java/org/apache/geode/internal/offheap/FreeListManagerTest.java