HFile intermediate block level indexes might recurse forever creating multi TB files

Mighty elserj was debugging an opentsdb cluster where some region directory ended up having 5TB+ files under <regiondir>/.tmp/

Further debugging and analysis, we were able to reproduce the problem locally where we never we recursing in this code path for writing intermediate level indices:

if (curInlineChunk != null) {
        while (rootChunk.getRootSize() > maxChunkSize) {
          rootChunk = writeIntermediateLevel(out, rootChunk);
          numLevels += 1;
        }
      }

The problem happens if we end up with a very large rowKey (larger than "hfile.index.block.max.size" being the first key in the block, then moving all the way to the root-level index building. We will keep writing and building the next level of intermediate level indices with a single very-large key. This can happen in flush / compaction / region recovery causing cluster inoperability due to ever-growing files.

Seems the issue was also reported earlier, with a temporary workaround:
https://github.com/OpenTSDB/opentsdb/issues/490