Negative request num in region load

We found that the request number of region is negative in long-running hbase cluster.
The is because of improper cast in HRegionServer#createRegionLoad

  ...
  .setReadRequestsCount((int)r.readRequestsCount.get())
  .setWriteRequestsCount((int) r.writeRequestsCount.get()) 

The patch is simple and just removes the cast.