HBASE-5533 metrics miss all operations submitted via MultiAction

A client application (LoadTestTool) calls put() on HTables. Internally to the HBase client those puts are batched into MultiActions. The total number of put operations shown in the RegionServer's put metrics histogram never increases from 0 even though millions of such operations are made. Needless to say the latency for those operations are not measured either. The value of HBASE-5533 metrics are suspect given the client will batch put and delete ops like this.

I had a fix in progress but HBASE-6284 messed it up. Before, MultiAction processing in HRegionServer would distingush between puts and deletes and dispatch them separately. It was easy to account for the time for them. Now both puts and deletes are submitted in batch together as mutations.