IndexTool should report the number of rows built

In the old design, the IndexTool MR job mapper first scanned the data table rows one by one using a Phoenix client code, then constructed the index rows and finally sent these row mutations to region servers to update the rows on the index table regions. While doing that, it emitted the counters at the row level. In the new design, this entire process is done on the server side (within a coprocessor). So, the mapper just issues one RPC call to instruct the coprocessor to build the entire table region. Thus, currently it does not report the number of rows that have been built, instead it reports the number of table regions built.